U.S. patent number RE42,112 [Application Number 11/652,468] was granted by the patent office on 2011-02-08 for chip light emitting diode and fabrication method thereof.
This patent grant is currently assigned to Seoul Semiconductor Co., Ltd.. Invention is credited to Kwan-Young Han, Do-Hyung Kim, Hong-San Kim, Chung-Hoon Lee, Kwang-Il Park, Seung-Man Yang.
United States Patent |
RE42,112 |
Han , et al. |
February 8, 2011 |
Chip light emitting diode and fabrication method thereof
Abstract
A chip light emitting diode having a wide viewing angle, and a
fabrication method thereof. The chip light emitting diode has a
resin package sealing a light emitting chip which has at least one
curved projecting part. The curved projecting part has a cross
section which is substantially semicircular, or substantially or
partially elliptical or parabolic. The curved projecting part
preferably has a cross section which is comprised of a plurality of
straight lines, an angle being formed between adjacent lines. The
cross section is elongated to form a cylindrical outer surface of
the resin package.
Inventors: |
Han; Kwan-Young (Seoul,
KR), Kim; Do-Hyung (Suwon, KR), Yang;
Seung-Man (Seoul, KR), Lee; Chung-Hoon (Seoul,
KR), Kim; Hong-San (Seongnam, KR), Park;
Kwang-Il (Seoul, KR) |
Assignee: |
Seoul Semiconductor Co., Ltd.
(Seoul, KR)
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Family
ID: |
34084287 |
Appl.
No.: |
11/652,468 |
Filed: |
January 11, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
10754389 |
Jan 9, 2004 |
07042022 |
May 9, 2006 |
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Foreign Application Priority Data
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Jul 25, 2003 [KR] |
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2003-51365 |
Aug 19, 2003 [KR] |
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2003-57331 |
Aug 20, 2003 [KR] |
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2003-57625 |
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Current U.S.
Class: |
257/99; 257/100;
257/433; 257/E33.066 |
Current CPC
Class: |
H01L
33/54 (20130101); H01L 2924/1815 (20130101); H01L
33/486 (20130101); H01L 2224/48091 (20130101); H01L
2224/48091 (20130101); H01L 2924/00014 (20130101) |
Current International
Class: |
H01L
29/22 (20060101) |
Field of
Search: |
;257/98-100,433,E33.066,101 ;438/22 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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48-012802 |
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Jan 1973 |
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JP |
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01-068200 |
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Jan 1991 |
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JP |
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06-112536 |
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Apr 1994 |
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JP |
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09-153646 |
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Jun 1997 |
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JP |
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2000-058925 |
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Feb 2000 |
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JP |
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2001-177156 |
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Jun 2001 |
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JP |
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2002-141558 |
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May 2002 |
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JP |
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2002-164583 |
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Jun 2002 |
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JP |
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2002-299697 |
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Oct 2002 |
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JP |
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2003-204083 |
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Jul 2003 |
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JP |
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2003/040784 |
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May 2003 |
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WO |
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Other References
Advisory Action dated Sep. 23, 2005 in U.S. Appl. No. 10/754,389.
cited by other .
Final Office Action dated Jul. 12, 2005 in U.S. Appl. No.
10/754,389. cited by other .
Non-Final Office Action dated Nov. 1, 2004 in U.S. Appl. No.
10/754,389. cited by other .
Notice of Allowance dated Dec. 20, 2005 in U.S. Appl. No.
10/754,389. cited by other.
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Primary Examiner: Ha; Nathan W
Attorney, Agent or Firm: H.C. Park & Associates, PLC
Claims
What is claimed is:
1. A chip light emitting diode comprising: a metal pad and a lead
spaced away from each other on a printed circuit board; a light
emitting chip mounted on the metal pad; a wire connecting the light
emitting chip and the lead; and a resin package sealing the light
emitting chip and at least a part of the metal pad, lead, and the
wire, the resin package having at least one curved projecting part,
the at least one curved projecting part having a cross section
elongated along the printed circuit board, wherein the cross
section of the curved projecting part is comprised of a plurality
of straight lines with an angle formed between adjacent lines.
2. A chip light emitting diode as recited in claim 1, wherein the
cross section of the curved projecting part is substantially
semicircular, or substantially or partially elliptical or
parabolic.
3. A chip light emitting diode as recited in claim 1, wherein at
least one stepped part is formed at an outer edge of the resin
package.
4. A chip light emitting diode as recited in claim 1, wherein the
surface of the resin package has fine striations to scattering
light emitted from the light emitting chip.
5. A chip light emitting diode as recited in claim 1, wherein the
resin package has one projecting part.
6. A chip light emitting diode as recited in claim 1, wherein the
resin package has two projecting parts which are spaced away from
each other by a predetermined interval, wherein the predetermined
interval ranges from 0.1 to 0.4 times a bottom length of the resin
package.
.Iadd.7. A chip light emitting diode comprising: a metal pad and a
lead spaced away from each other on a printed circuit board; a
light emitting chip mounted on the metal pad; a wire connecting the
light emitting chip and the lead; and a resin package sealing the
light emitting chip and at least a part of the metal pad, lead, and
the wire, the resin package having at least one curved projecting
part, the at least one curved projecting part having a
cross-section elongated along the printed circuit board and wherein
at least one stepped part is formed at an outer edge of the resin
package..Iaddend.
.Iadd.8. A chip light emitting diode as recited in claim 7, wherein
the cross-section of the curved projecting part is substantially
semicircular, or substantially or partially elliptical or
parabolic..Iaddend.
.Iadd.9. A chip light emitting diode as recited in claim 7, wherein
the surface of the resin package has fine striations to scatter
light emitted from the light emitting chip..Iaddend.
.Iadd.10. A chip light emitting diode as recited in claim 7,
wherein the resin package has one projecting part..Iaddend.
.Iadd.11. A chip light emitting diode as recited in claim 7,
wherein the resin package has two projecting parts which are spaced
away from each other by a predetermined interval; wherein the
predetermined interval ranges from 0.1 to 0.4 times a bottom length
of the resin package..Iaddend.
.Iadd.12. A chip light emitting diode comprising: a metal pad and a
lead spaced away from each other on a printed circuit board; a
light emitting chip mounted on the metal pad; a wire connecting the
light emitting chip and the lead; and a resin package sealing the
light emitting chip and at least a part of the metal pad, lead, and
the wire, the resin package having at least one curved projecting
part, the at least one curved projecting part having a
cross-section elongated along the printed circuit board and wherein
the surface of the resin package has fine striations to scatter
light emitted from the light emitting chip..Iaddend.
.Iadd.13. A chip emitting diode as recited in claim 12, wherein the
cross-section of the curved projecting part is substantially
semicircular, or substantially or partially elliptical or
parabolic..Iaddend.
.Iadd.14. A chip emitting diode as recited in claim 12, wherein the
resin package has two projecting parts which are spaced away from
each other by a predetermined interval; wherein the predetermined
interval ranges from 0.1 to 0.4 times a bottom length of the resin
package..Iaddend.
.Iadd.15. A chip light emitting diode comprising: a metal pad and a
lead spaced away from each other on a printed circuit board; a
light emitting chip mounted on the metal pad; a wire connecting the
light emitting, chip and the lead; and a resin package sealing the
light emitting chip and at least a part of the metal pad, lead, and
the wire, the resin package having at least one curved projecting
part, the at least one curved projecting part having a
cross-section elongated along the printed circuit board; wherein
the resin package has two projecting parts which are spaced away
from each other by a predetermined interval; and wherein the
predetermined interval ranges from 0.1 to 0.4 times a bottom length
of the resin package..Iaddend.
.Iadd.16. A chip emitting diode as recited in claim 15, wherein the
cross-section of the curved projecting part is substantially
semicircular, or substantially or partially elliptical or
parabolic..Iaddend.
.Iadd.17. A chip light emitting diode as recited in claim 15,
wherein the resin package has one projecting part..Iaddend.
.Iadd.18. A chip light emitting diode comprising: a metal pad and a
lead spaced away from each other on a printed circuit board; a
light emitting chip mounted on the metal pad; a wire connecting the
light emitting chip and the lead; and a resin package sealing the
light emitting chip and at least a part of the metal pad, lead, and
the wire, the resin package having at least one curved projecting
part, the at least one curved projecting part having a
cross-section elongated along the printed circuit board and wherein
one stepped part is formed at an outer edge of the resin
package..Iaddend.
.Iadd.19. A chip light emitting diode as recited in claim 18,
wherein the cross-section of the curved projecting part is
substantially semicircular, or substantially or partially
elliptical or parabolic..Iaddend.
.Iadd.20. A chip light emitting diode as recited in claim 18,
wherein the surface of the resin package has fine striations to
scatter light emitted from the light emitting chip..Iaddend.
.Iadd.21. A chip light emitting diode as recited in claim 18,
wherein the resin package has one projecting part..Iaddend.
.Iadd.22. A chip light emitting diode as recited in claim 18,
wherein the resin package has two projecting parts which are spaced
away from each other by a predetermined interval; wherein the
predetermined interval ranges from 0.1 to 0.4 times a bottom length
of the resin package..Iaddend.
.Iadd.23. A chip light emitting diode comprising: a metal pad and a
lead spaced away from each other on a printed circuit board; a
light emitting chip mounted on the metal pad; a wire connecting the
light emitting chip and the lead; a resin package sealing the light
emitting chip and at least a part of the metal pad, lead, and the
wire, the resin package having at least one curved projecting part,
the at least one curved projecting part having a cross-section
elongated along the printed circuit board and wherein the
cross-section of the curved projecting part is substantially
semicircular, or substantially or partially elliptical or parabolic
and at least one stepped part being formed at an outer edge of the
resin package..Iaddend.
.Iadd.24. A chip light emitting diode as recited in claim 23,
wherein the surface of the resin package has fine striations to
scatter light emitted from the light emitting chip..Iaddend.
.Iadd.25. A chip light emitting diode as recited in claim 23,
wherein the resin package has one projecting part..Iaddend.
.Iadd.26. A chip light emitting diode as recited in claim 23,
wherein the resin package has two projecting parts which are spaced
away from each other by a predetermined interval; wherein the
predetermined interval ranges from 0.1 to 0.4 times a bottom length
of the resin package..Iaddend.
.Iadd.27. A chip light emitting diode comprising: a metal pad and a
lead spaced away from each other on a printed circuit board; a
light emitting chip mounted on the metal pad; a wire connecting the
light emitting chip and the lead; and a resin package sealing the
light emitting chip and at least a part of the metal pad, lead, and
the wire, the resin package having at least one curved projecting
part, the at least one curved projecting part having a
cross-section elongated along the printed circuit board wherein at
least one stepped part is formed at an outer edge of the resin
package and wherein the surface of the resin package has fine
striations to scatter light emitted from the light emitting
chip..Iaddend.
.Iadd.28. A chip light emitting diode as recited in claim 27,
wherein the cross-section of the curved projecting part is
substantially semicircular, or substantially or partially
elliptical or parabolic..Iaddend.
.Iadd.29. A chip light emitting diode as recited in claim 27,
wherein the resin package has one projecting part..Iaddend.
.Iadd.30. A chip light emitting diode as recited in claim 27,
wherein the resin package has two projecting parts which are spaced
away from each other by a predetermined interval; wherein the
predetermined interval ranges from 0.1 to 0.4 times a bottom length
of the resin package..Iaddend.
.Iadd.31. A chip light emitting diode comprising: a metal pad and a
lead spaced away from each other on a printed circuit board; a
light emitting chip mounted on the metal pad; a wire connecting the
light emitting chip and the lead; a resin package sealing the light
emitting chip and at least a part of the metal pad, lead, and the
wire, the resin package having at lest one curved projecting part,
the at least one curved projecting part having a cross-section
elongated along the printed circuit board, wherein at least one
stepped part is formed at an outer edge of the resin package and
wherein the resin package has two projecting parts which are spaced
away from each other by a predetermined interval..Iaddend.
.Iadd.32. A chip light emitting diode as recited in claim 31,
wherein the cross-section of the curved projecting part is
substantially semicircular, or substantially or partially
elliptical or parabolic..Iaddend.
.Iadd.33. A chip light emitting diode as recited in claim 31,
wherein the surface of the resin package has fine striations to
scatter light emitted from the light emitting chip..Iaddend.
.Iadd.34. A chip light emitting diode as recited in claim 31,
wherein the predetermined interval ranges from 0.1 to 0.4 times a
bottom length of the resin package..Iaddend.
.Iadd.35. A chip light emitting diode comprising: a metal pad and a
lead spaced away from each other on a printed circuit board; a
light emitting chip mounted on the metal pad; a wire connecting the
light emitting chip and the lead; and a resin package sealing the
light emitting chip and at least a part of the metal pad, lead, and
the wire, the resin package having at least one curved projecting
part, the at least one curved projecting part having a
cross-section elongated along the printed circuit board, wherein
the cross-section of the curved projecting part is substantially
semicircular, or substantially or partially elliptical or
parabolic, and wherein the surface of the resin package has fine
striations to scatter light emitted from the light emitting
chip..Iaddend.
.Iadd.36. A chip light emitting diode comprising: a metal pad and a
lead spaced away from each other on a printed circuit board; a
light emitting chip mounted on the metal pad; a wire connecting the
light emitting chip and the lead; and a resin package sealing the
light emitting chip and at least a part of the metal pad, led, and
the wire, the resin package having at least one curved projecting
part, the at least one curved projecting part having a
cross-section elongated along the printed circuit board, wherein
the surface of the resin package has fine striations to scatter
light emitted from the light emitting chip and wherein the resin
package has one projecting part..Iaddend.
.Iadd.37. A chip light emitting diode comprising: a metal pad and a
lead spaced away from each other on a printed circuit board; a
light emitting chip mounted on the metal pad; a wire connecting the
light emitting chip and the lead; a resin package sealing the light
emitting chip and at least a part of the metal pad, lead, and the
wire, the resin package having at least one curved projecting part,
the at least one curved projecting part having a cross-section
elongated along the printed circuit board, wherein the surface of
the resin package has fine striations to scatter light emitted from
the light emitting chip and wherein the resin package has two
projecting parts which are spaced away from each other by a
predetermined interval..Iaddend.
.Iadd.38. A chip light emitting diode as recited in claim 37,
wherein the predetermined interval ranges from 0.1 to 0.4 times a
bottom length of the resin package..Iaddend.
.Iadd.39. A chip light emitting diode comprising: a metal pad and a
lead spaced away from each other on a printed circuit board; a
light emitting chip mounted on the metal pad; a wire connecting the
light emitting chip and the lead; a resin package sealing the light
emitting chip and at least a part of the metal pad, lead, and the
wire, the resin package having at least one curved projecting part,
the at least one curved projecting part, the at least one curved
projecting part having a cross-section elongated along the printed
circuit board wherein the cross-section of the curved projecting
part is substantially semicircular, or substantially or partially
elliptical or parabolic and wherein the resin package has two
projecting parts which are spaced away from each other by a
predetermined interval..Iaddend.
.Iadd.40. A light emitting diode as recited in claim 39 wherein the
predetermined interval ranges from 0.1 to 0.4 times a bottom length
of the resin package..Iaddend.
Description
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a chip light emitting diode and a
fabrication method thereof.
(b) Description of the Related Art
Chip light emitting diodes (LEDs) are generally employed as display
devices and for backlighting. Recently, their use range has been
increased to include various applications such as light sources for
mobile phones and personal digital assistants (PDAs).
Referring to FIG. 1, a conventional chip LED 50 is provided with a
metal pad 52 and a lead 55 on a printed circuit board (PCB) 51. A
light emitting chip 53 mounted on the metal pad 52 is connected to
the lead 55 via a wire 54. A resin package 56 is formed of an epoxy
mold compound (EMC), and seals the chip 53.
The conventional chip LED 50 has drawbacks in that optical paths of
emitted light rays are limited because the resin package 56 has a
rectangular cross section, causing a narrow viewing angle of the
chip LED. Further, the intensity distribution of the emitted light
is concentrated at the position of the chip. Therefore, many chip
LEDs are required to light a certain area, resulting in high
manufacturing cost in some applications such as for
backlighting.
Further, heat generated from the conventional chip LED 50 during
operation is concentrated in the edges, resulting in thermal or
mechanical deformation of the diode.
When the thickness of the resin package is reduced for overall
compactness of the conventional chip LED, a metal mold of the resin
package should be more precisely formed for the edges, which may
result in high manufacturing costs. Further, when the thickness of
the resin package happens to be not uniform, stress may be
concentrated at a thin part, so the adhesive strength is
deteriorated causing poor reliability of the chip LED.
SUMMARY OF THE INVENTION
In view of the prior art described above, it is an object of the
present invention to provide a chip light emitting diode (LED)
having a wide viewing angle and a fabrication method thereof.
It is another object of the present invention to provide a chip LED
in which the light intensity is substantially uniform on either
side in order to illuminate a larger area with high brightness.
It is another object of the present invention to provide a chip LED
in which the heat generated is distributed uniformly to avoid
thermal and mechanical deformation and to prevent stress from
centralizing on one side.
It is still another object of the present invention to provide a
fabrication method of a chip LED, in which a simple metal mold
structure can be employed to reduce fabrication costs.
To achieve these and other objects, as embodied and broadly
described herein, a chip light emitting diode includes:
a metal pad and a lead spaced away from each other on a printed
circuit board;
a light emitting chip mounted on the metal pad;
a wire connecting the light emitting chip and the lead; and
a resin package sealing the light emitting chip and at least a part
of the metal pad, the lead, and the wire, the resin package having
at least one curved projecting part.
The curved projecting part has a cross section which is
substantially semicircular, or substantially or partially
elliptical or parabolic. The curved projecting part preferably has
a cross section which is comprised of a plurality of straight
lines, an angle being formed between adjacent lines.
According to another aspect of the present invention, a fabrication
method of a chip light emitting diode comprises the steps of:
mounting a light emitting chip on a metal pad formed on a printed
circuit board;
connecting the light emitting chip to a lead formed on the printed
circuit board;
providing the printed circuit board within a mold having a cavity,
the cavity corresponding to at least one projecting part of the
chip light emitting diode; and
forming a resin package sealing the light emitting chip and at
least a part of the metal pad and lead by injecting resin material
into the cavity of the mold, the resin package having at least one
curved projecting part.
Both the foregoing general description and the following Detailed
Description are exemplary and are intended to provide further
explanation of the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings provide a further understanding of the
invention and, together with the Detailed Description, explain the
principles of the invention. In the drawings:
FIG. 1 is a perspective view of a conventional chip light emitting
diode;
FIG. 2 is a perspective view of a chip light emitting diode
according to a first preferred embodiment;
FIG. 3 is an enlarged sectional view taken along lines A--A of FIG.
2;
FIGS. 4a and 4b shows characteristics of viewing angle according to
the chips of FIG. 2 and FIG. 1, respectively;
FIGS. 5 to 7 show other examples of the resin package in the chip
light emitting diodes according to the first preferred
embodiment;
FIG. 8 is a perspective view of a chip light emitting diode
according to a second preferred embodiment;
FIG. 9 is a sectional view along lines A--A of FIG. 8;
FIGS. 10 and 11 show other examples of the resin package in the
chip light emitting diodes according to the second preferred
embodiment; and
FIG. 12 shows a flow chart illustrating a fabricating method of a
chip light emitting diode according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be described in detail with reference to
the accompanying drawings.
Referring to FIGS. 2 and 3, a chip light emitting diode (LED) 100
according to a first preferred embodiment of the present invention
has a metal pad 120 and a lead 150 provided on a printed circuit
board (PCB) 110, and a light emitting chip 130 mounted on the metal
pad 120. The metal pad 120 is made of an electrically conductive
material, and the chip 130 may be suitably selected from among
light emitting chips of wavelengths ranging from infrared to
ultraviolet. A wire 140 connects the light emitting chip 130 to the
lead 150, and a resin package is formed protruding from the PCB 110
to seal the chip 130 and parts of the lead 150 and metal pad
120.
The resin package 160 has a curved projecting part 161 which has a
cross section that is substantially semicircular. The cross section
is elongated to form a cylindrical outer surface of the resin
package 160. A suitable epoxy resin may be injected and molded into
the resin package 160 using a metal mold (not shown) with a curved
cavity.
Light rays R emitted by the chip 130 are refracted on the gently
curved surface with different refractive angles. This causes light
intensity distribution to become uniform and the viewing angle to
be wide.
As shown in the enlarged sectional view of FIG. 3, the surface of
the resin package 160 may have fine striations to scatter light
emitted from the chip 130. The striations may be formed with a
triangular shape, a sinusoidal wave shape, or another suitable
shape. The period p of the striations preferably ranges from about
0.5 .mu.m to 1.0 .mu.m. The striations may scatter the light
emitted by the chip 130 during refraction on the surface of the
resin package 160 to further widen the viewing angle.
As shown in FIGS. 4A and 4B, in which the viewing angles of the
chip LED 100 according to the present invention and the
conventional chip LED 50 are respectively shown, the chip LED 100
has a viewing angle ranging about 160.degree. from H(a) to H(b)
shown in a bold line, while the conventional chip LED 50 has a
viewing angle ranging about 120.degree. from H(a') to H(b'), under
the same experimental conditions. Therefore, it is noted that the
viewing angle of the chip LED 100 according to the present
invention is enhanced by about 400 with respect to the conventional
chip LED 50
The resin package 160 of the chip LED 100 has no sharp edge, but
rather it has a gently curved surface without limitation of the
light path. This causes the light efficiency to be increased, as
confirmed by experimental results shown in TABLE 1 which were
obtained by the inventors through many experiments. TABLE 1 shows
only average values of the light intensity and brightness according
to the chip LED 100 and the conventional chip LED 50.
TABLE-US-00001 TABLE 1 Average light intensity Average Brightness
(mcd) (cd/m.sup.2) Chip LED according to the 26 980 first preferred
embodiment Conventional ship LED 20 700
The experimental results of TABLE 1 were measured under the
condition that the light emitting chips 100, 50 had the same
dimensions of 304 .mu.m in width, 304 .mu.m in depth, and 100 .mu.m
in height, and input currents of 5 mA in light intensity
measurement and 15 mA in brightness measurement.
Referring to TABLE 1, the chip LED 100 according to the present
invention is enhanced in light intensity by 6 mcd and in brightness
by 280 cd/m' on average with respect to the conventional chip LED
50. Therefore, it is noted that the chip LED 100 has more light
efficiency than the conventional one.
The curved projecting part 161 of the resin package 160 is
described having a cross section of a semicircle referring to FIGS.
2 and 3, but it is not limited thereto. The cross section of the
curved projecting part 161 may be variably modified. FIGS. 5 to 7
shows examples of chip LEDs having resin packages of various cross
sections.
Referring now to FIG. 5, the chip LED 200 has a resin package 260.
The resin package 260 has a curved projecting part 261 which has a
cross section that is substantially semicircular, similar to that
of FIG. 2 or FIG. 3. Further, the cross section of the curved
projecting part 261 is comprised of a plurality of straight lines
with an angle .theta. formed between adjacent lines. The angle
.theta. may be the same over the entire curvature, or different
depending on location. The cross section is elongated to form a
cylindrical outer surface of the resin package 260. The resin
package 260 may serve a similar function as the resin package 160
according to the first preferred embodiment.
Referring to FIG. 6, a resin package 360 of a chip LED 300 has a
stepped part 390 along edges on the elongated sides. The resin
package 360 has a curved projecting part 361 to serve a similar
function as the resin package 160 according to the first preferred
embodiment. Although one stepped part is formed on each side in
FIG. 6, it is possible to provide two or more stepped parts on each
side as necessary.
It is also possible to provide a chip LED 400 with a resin package
460, as shown in FIG. 7, whose upper surface is curved while side
surfaces thereof are flat.
The present invention is not limited to the above-described
embodiments. A curved projecting part of the resin package may have
a cross section that is partly elliptical, parabolic, or circular,
or any modification thereof. A surface of the resin package may
have fine striations to scatter light, resulting in further
widening of the range of viewing angle.
The resin package according to the present invention may be easily
adapted to chip LEDs having a two-top structure.
Referring next to FIGS. 8 and 9, a chip LED 600 according to a
second preferred embodiment of the present invention will be
described. The chip LED 600 is similar to the chip LED 100
according to the first preferred embodiment, except the shape of a
resin package 660.
The resin package 660 of the chip LED 600 has two curved projecting
parts 661, 662. Both curved projecting parts 661, 662 are spaced
out by spacer 663 with an interval 1 therebetween. The interval 1
may be selected from a range of 0.1 to 0.4 times the bottom length
b in the cross section.
In the chip LED 600 according to the second preferred embodiment,
light rays emitted by the chip 130 are transmitted and refracted on
the two curved surface of the projecting parts 661 and 662. Then,
the refracted rays diverge to provide a large viewing angle. This
may enhance the lighting effect of both sides on a predetermined
area.
Although the resin package 660 of the chip LED 600 according to the
second preferred embodiment is described to have two projecting
parts 661, 662, it is also possible to form more than two
projecting parts in a resin package.
FIGS. 10 and 11 show other examples of the resin package. A chip
LED 700 of FIG. 10 has a resin package 760 with two projecting
parts 761, 762 which are formed adjacent to each other without any
spacer. A chip LED 800 having a resin package 860 is shown in FIG.
11. Three projecting parts 861, 862, 863 are formed with two
spacers 864, 865.
Light rays emitted by the chip 130 in the chip LED 700 or 800 are
transmitted and refracted in the projecting parts 661, and they
diverge with a large viewing angle. This may enhance the lighting
effect as compared to the conventional chip LED 50 in FIG. 1.
It is also possible that the surface of the resin package according
to the second preferred embodiment may have fine striations to
scatter light, resulting in further widening of the range of
viewing angle.
Referring next to FIG. 12 with FIG. 2, a fabrication method of a
chip LED will be described. First, the metal pad 120 and lead 150
are formed on the PCB 110 (S1). The chip 130 is mounted on the
metal pad 120 and then connected to the lead 150 with the wire 140
(S2-S3). The chip 130 may be suitably selected from among light
emitting chips of a desired wavelength.
The PCB 110 is then mounted on a mold having a cavity (S4). The
cavity corresponds to the projecting part(s) according to one of
the first preferred embodiment and the second preferred
embodiment.
Next, a solid epoxy mold compound is heated to 170-1800 and
injected into the mold. The resin package 160 is formed on the PCB
110 with the shape described in the first or second preferred
embodiment (S5). The resin package is formed to seal the light
emitting chip. It is possible that the resin package is formed to
seal either a part of the metal pad and lead, or the entire surface
of the metal pad and lead.
Practically, a plurality of chip LEDs are formed on one PCB, which
for example has a size of about 80 mm.times.50 mm. Therefore, each
chip LED on the PCB is individually cut off (S6).
As described above, light rays emitted from the light emitting chip
diverge radially and uniformly in a chip LED according to the
present invention, to further widen the viewing angle. The lighting
efficiency of the chip LED is also improved, so the number of chip
LEDs is reduced in application to backlighting to light a certain
area.
Heat generated from the chip LED according to the present invention
is also uniformly distributed on the surface, to prevent the chip
LED from deforming thermally or mechanically. Further, stress is
not concentrated on one side, to enhance the adhesive
characteristics between the resin package and the PCB, especially
in compact chip LEDs.
Since a mold with a curved projecting part is easily manufactured,
as compared to a resin package with a rectangular cross section, a
relatively simple mold structure for a resin package reduces
fabrication costs.
It will be apparent to those skilled in the art that various
modifications and variations can be made to the device and method
of the present invention without departing from the spirit and
scope of the invention. The present invention covers the
modifications and variations of this invention provided they come
within the scope of the appended claims and their equivalents.
* * * * *