U.S. patent application number 11/429235 was filed with the patent office on 2007-03-29 for light emitting device.
This patent application is currently assigned to Industrial Technology Research Institute. Invention is credited to Sheng-Pan Huang, Chia-Chang Kuo, Ming-Te Lin, Ming-Yao Lin, Wen-Yung Yeh.
Application Number | 20070069219 11/429235 |
Document ID | / |
Family ID | 37832775 |
Filed Date | 2007-03-29 |
United States Patent
Application |
20070069219 |
Kind Code |
A1 |
Lin; Ming-Te ; et
al. |
March 29, 2007 |
Light emitting device
Abstract
A light emitting device is proposed, which emits light while
connected to the power. The light emitting device includes a light
emitting element having at least two electrodes disposed at the
side of the light output surface thereof; and a base member having
a recess and lead portions corresponding to the electrodes, the
light emitting element being mounted on the base member and
received in the recess, wherein the light output surface faces
toward opening of the recess that becomes smaller while approaching
the light output surface, and the electrodes are respectively in
electrical connection with the lead portions that extend from the
connection positions to outer edge of the base member for power
connection. The light emitting device of the present invention has
advantages of short current path, low series thermal resistance and
low cost. In addition, the depth of the recess can further be
increased to improve light collecting efficiency.
Inventors: |
Lin; Ming-Te; (Hsinchu
Hsien, TW) ; Lin; Ming-Yao; (Hsinchu Hsien, TW)
; Kuo; Chia-Chang; (Hsinchu Hsien, TW) ; Huang;
Sheng-Pan; (Hsinchu Hsien, TW) ; Yeh; Wen-Yung;
(Hsinchu Hsien, TW) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
Industrial Technology Research
Institute
|
Family ID: |
37832775 |
Appl. No.: |
11/429235 |
Filed: |
May 8, 2006 |
Current U.S.
Class: |
257/79 ;
257/E33.072 |
Current CPC
Class: |
H01L 2224/16 20130101;
H01L 2924/01079 20130101; H01L 2924/01068 20130101; H01L 2924/00014
20130101; H01L 33/60 20130101; H01L 33/642 20130101; H01L
2224/48091 20130101; H01L 33/62 20130101; H01L 2224/48091
20130101 |
Class at
Publication: |
257/079 |
International
Class: |
H01L 33/00 20060101
H01L033/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 28, 2005 |
TW |
094133671 |
Claims
1. A light emitting device, at least comprising: a light emitting
element having at least two electrodes disposed at a side of a
light output surface thereof; a base member comprising a recess and
a plurality of lead portions corresponding to the electrodes, the
light emitting element being mounted on the base member and
received in the recess, wherein the light output surface faces
toward an opening of the recess that converges while approaching
the light output surface, and the electrodes are respectively in
electrical connection with the lead portions that extend from the
connection positions to outer edge of the base member for power
connection.
2. The light emitting device of claim 1, wherein the light emitting
element comprises at least one substrate provided with electrodes
for power connection and at least one light emitting chip mounted
on the substrate and electrically connected with the substrate.
3. The light emitting device of claim 1 or 2, wherein the light
emitting element is selected from the group consisting of single
color single chip, single color multi-chip, multi-color multi-chip
and chip(s) emitting ultraviolet light.
4. The light emitting device of claim 2, wherein the light emitting
chip in a flip-chip configuration is electrically connected with
the substrate via one of the group consisting of gold balls, tin
balls and electrically and thermally conductive material.
5. The light emitting device of claim 2, wherein the light emitting
chip is an LED chip.
6. The light emitting device of claim 2, wherein the substrate is
selected from the group consisting of Si, Al and C.
7. The light emitting device of claim 1, wherein the base member is
a lead frame.
8. The light emitting device of claim 7, wherein the lead frame is
formed by one of the methods consisting of injection molding and
assembly.
9. The light emitting device of claim 7, wherein the lead frame is
mainly formed of one of the group consisting of PPA resin, PC
thermoplastic material and insulating material.
10. The light emitting device of claim 1, wherein a light
reflecting portion is further disposed in the recess adjacent to
the light output surface such that the light emitted from the light
emitting element can be reflected to walls of the recess to form a
substantially collimated light beam so as to improve light
efficiency.
11. The light emitting device of claim 10, wherein the light
reflecting portion is formed of reflective material by one of the
methods consisting of electroplating and assembling.
12. The light emitting device of claim 1, wherein a light
converting portion is further disposed in the recess adjacent to
the light output surface to change the wavelength of the light
emitted from the light emitting element so as to improve light
efficiency.
13. The light emitting device of claim 12, wherein the light
converting portion is formed of fluorescent converting material by
coating.
14. The light emitting device of claim 10, wherein the recess is
filled with sealing member to fix the light reflecting portion and
the light emitting element to the base member.
15. The light emitting device of claim 12, wherein the recess is
filled with sealing member to fix the light converting portion and
the light emitting element to the base member.
16. The light emitting device of claim 15, wherein the sealing
member further forms a lens shape at the light output surface of
the light emitting element to improve light collecting
efficiency.
17. The light emitting device of claim 1, wherein the lead portions
are formed of electrically conductive conductor.
18. The light emitting device of claim 17, wherein the conductor is
one of the group consisting of Au, Ag, Cu, Sn, Al and conductive
material.
19. The light emitting device of claim 1 or 17, wherein the lead
portions are electrically connected with the electrodes of the
light emitting element through one of the group consisting of
conductive adhesive, gold balls, tin balls and conductive bonding
material.
20. The light emitting device of claim 19, wherein the conductive
adhesive is one of the group consisting of silver paste, solder
paste and solder paste containing lead.
21. The light emitting device of claim 1 further includes a thermal
conductor attached to a surface of the light emitting element
opposite to the light output surface for heat dissipation.
22. The light emitting device of claim 21, wherein the thermal
conductor is formed of one of the group consisting of Al, Cu, Fe
and material having a thermal conductivity of at least 50 W/mK.
23. The light emitting device of claim 21, wherein an adhesive
layer is further disposed between the thermal conductor and the
light emitting element.
24. The light emitting device of claim 23, wherein the adhesive
layer is formed of heat sink paste.
25. A light emitting device, comprising: a light emitting element
having at least two electrodes disposed at the side of the light
output surface thereof; a base member having a recess and lead
portions corresponding to the electrodes, the light emitting
element being mounted on the base member and received in the
recess, wherein the light output surface faces toward opening of
the recess that becomes smaller while approaching the light output
surface, and the electrodes are respectively in electrical
connection with the lead portions that extend from the connection
positions to outer edge of the base member for power connection,
and a light reflecting portion is disposed in the recess adjacent
to the light output surface such that the light emitted from the
light emitting element can be reflected to walls of the recess to
form a substantially collimated light beam so as to improve light
efficiency, the recess being filled with sealing member to fix the
light reflecting portion and the light emitting element to the base
member; and a thermal conductor attached to a surface of the light
emitting element opposite to the light output surface for heat
dissipation.
26. The light emitting device of claim 25, wherein the light
emitting element comprises at least one substrate provided with
electrodes for power connection and at least one light emitting
chip mounted on the substrate and electrically connected with the
substrate.
27. The light emitting device of claim 25 or 26, wherein the light
emitting element comprises one of the group consisting of single
color single chip, single color multi-chip, multi-color multi-chip
and chip(s) emitting ultraviolet light.
28. The light emitting device of claim 26, wherein the light
emitting chip in a flip-chip configuration is electrically
connected with the substrate via one of the group consisting of
gold balls, tin balls and electrically and thermally conductive
material.
29. The light emitting device of claim 26 or 8, wherein the light
emitting chip is an LED chip.
30. The light emitting device of claim 26, wherein the substrate is
made of one of the group consisting of Si, Al and C.
31. The light emitting device of claim 25, wherein the base member
is a lead frame.
32. The light emitting device of claim 31, wherein the lead frame
is formed by one of the methods consisting of injection molding and
assembly.
33. The light emitting device of claim 31 or 32, wherein the lead
frame is mainly formed of one of the group consisting of PPA resin,
PC thermoplastic material and insulating material.
34. The light emitting device of claim 25, wherein the lead
portions are formed of electrically conductive conductor.
35. The light emitting device of claim 34, wherein the conductor is
one of the group consisting of Au, Ag, Cu, Sn, Al and conductive
material.
36. The light emitting device of claim 25 or 34, wherein the lead
portions are further electrically connected with the electrodes of
the light emitting element through one of the group consisting of
conductive adhesive, gold balls, tin balls and conductive bonding
material.
37. The light emitting device of claim 36, wherein the conductive
adhesive is one of the group consisting of silver paste, solder
paste and solder paste containing lead.
38. The light emitting device of claim 25, wherein the sealing
member forms a lens shape at the light output surface of the light
emitting element to improve light collecting efficiency.
39. The light emitting device of claim 25, wherein light reflecting
portion is formed of reflective material by one of the methods
consisting of electroplating and assembling.
40. The light emitting device of claim 25, wherein the thermal
conductor is formed of one of the group consisting of Al, Cu, Fe
and material having a thermal conductivity of at least 50 W/mK.
41. The light emitting device of claim 25, wherein an adhesive
layer is further disposed between the thermal conductor and the
light emitting element.
42. The light emitting device of claim 41, wherein the adhesive
layer is formed of heat sink paste.
43. A light emitting device, comprising: a light emitting element
with at least two electrodes disposed at the side of the light
output surface thereof; a base member having a recess and lead
portions corresponding to the electrodes, the light emitting
element being mounted on the base member and received in the
recess, wherein the light output surface faces toward opening of
the recess that becomes smaller while approaching the light output
surface, and the electrodes are respectively in electrical
connection with the lead portions that extend from the connection
positions to outer edge of the base member for power connection,
and a light converting portion is disposed in the recess adjacent
to the light output surface to change the wavelength of the light
emitted from the light emitting element so as to improve light
efficiency, the recess being filled with sealing member to fix the
light converting portion and the light emitting element to the base
member; and a thermal conductor attached to a surface of the light
emitting element opposite to the light output surface for heat
dissipation.
44. The light emitting device of claim 43, wherein the light
emitting element comprises at least one substrate provided with
electrodes for power connection and at least one light emitting
chip mounted on the substrate and electrically connected with the
substrate.
45. The light emitting device of claim 43, wherein the light
emitting element comprises one of the group consisting of single
color single chip, single color multi-chip, multi-color multi-chip
and chip(s) emitting ultraviolet light.
46. The light emitting device of claim 44, wherein the light
emitting chip in a flip-chip configuration is electrically
connected with the substrate via one of the group consisting of
gold balls, tin balls and electrically and thermally conductive
material.
47. The light emitting device of claim 44, wherein the light
emitting chip is an LED chip.
48. The light emitting device of claim 44, wherein the substrate is
made of one of the group consisting of Si, Al and C.
49. The light emitting device of claim 43, wherein the substrate is
a lead frame.
50. The light emitting device of claim 49, wherein the lead frame
is formed by one of the methods consisting of injection molding and
assembly.
51. The light emitting device of claim 49, wherein the lead frame
is mainly formed of one of the group consisting of PPA resin, PC
thermoplastic material and insulating material.
52. The light emitting device of claim 43, wherein the lead
portions are formed of electrically conductive conductor.
53. The light emitting device of claim 52, wherein the conductor is
one of the group consisting of Au, Ag, Cu, Sn, Al and conductive
material.
54. The light emitting device of claim 43 or 52, wherein the lead
portions are electrically connected with the electrodes of the
light emitting element through one of the group consisting of
conductive adhesive, gold balls, tin balls and conductive bonding
material.
55. The light emitting device of claim 54, wherein the conductive
adhesive is one of the group consisting of silver paste, solder
paste and solder paste containing lead.
56. The light emitting device of claim 43, wherein the sealing
member further forms a lens shape at the light output surface of
the light emitting element to improve light collecting
efficiency.
57. The light emitting device of claim 43, wherein the light
converting portion is formed of fluorescent converting material by
coating.
58. The light emitting device of claim 43, wherein the thermal
conductor is formed of one of the group consisting of Al, Cu, Fe
and material having a thermal conductivity of at least 50 W/mK.
59. The light emitting device of claim 43, wherein an adhesive
layer is further disposed between the thermal conductor and the
light emitting element.
60. The light emitting device of claim 59, wherein the adhesive
layer is formed of heat sink paste.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to light emitting devices and,
more particularly, to a light emitting device that can be applied
to high power light emitting diodes.
[0003] 2. Description of Related Art
[0004] Currently, light emitting diodes (LEDs) that are
characterized by long lifetime, small volume, low heat dissipation,
low power consumption, fast response speed and single color light
emission are widely used in indicator lights, bill boards, traffic
lights, auto lamps, display panels, communication tools, consumer
electronics and so on. Accordingly, different packaging techniques
are developed for LEDs packaging, which results in different
package structures of LEDs.
[0005] FIGS. 1(A) to 1(C) show a flip chip packaging process. As
shown in FIG. 1(A), a plurality of conductive bumps 11 is formed on
an aluminum substrate 10. Then, as shown in FIG. 1(B), an LED chip
12 is attached to the aluminum substrate 10 upside down. Finally,
underfill and package processes are performed and a final package
structure is shown in FIG. 1(C).
[0006] FIGS. 2(A) to 2(C) show a wire bonding packaging process. As
shown in FIG. 2(A), an aluminum substrate or ceramic substrate 20
is coated with silver paste 21. Then, as shown in FIG. 2(B), a flip
chip LED chip device 22 is attached to the substrate and wire
bonding process is performed. Subsequently, underfill and package
processes are performed and a final package structure is shown in
FIG. 2(C).
[0007] In the above two packaging processes, because the molding
compound and the substrate have different expansion factors,
deformation and stripping are easy to happen. In addition, since
the LED chip is electrically connected to the outside through the
aluminum or ceramic substrate, the conductive path is very long,
which results in too much heat absorption by the aluminum or
ceramic substrate, thereby making the mass production difficult.
Furthermore, if several chip products are applied to the aluminum
or ceramic substrate, the aluminum or ceramic substrate becomes so
weak that it needs to be processed before the reflow process,
thereby resulting in high fabrication cost.
[0008] FIGS. 3(A) to 3(C) and FIGS. 4(A) to 4(C) show two packaging
processes which respectively use lead frames 30 and 40 and heat
sinks 31 and 41. As shown in FIGS. 3(A) and 4(A), the heat sinks 31
and 41 located on the lead frames 30 and 40 are respectively coated
with silver paste 32 and 42. As shown in FIGS. 3(B) and 4(B), flip
chip LED chip devices 33 and 43 are respectively attached to the
lead frames 30 and 40. Afterwards, a wire bonding process is
performed. Subsequently, the underfill and package processes are
performed and final package structures are shown in FIGS. 3(C) and
4(C).
[0009] In the above two packaging processes, high series thermal
resistance leads to low reliability. Further, since the stack
technique is used in the above two packaging processes, the
packaged products become very thick. To facilitate processes that
are performed from the front side of the package structure, the
depth of the recess must be shallow (as shown in FIGS. 4(A) to
4(C)). However, such a shallow recess will affect light collecting
efficiency.
[0010] FIGS. 5(A) to 5(C) and FIGS. 6(A) to 6(C) show two packaging
processes which use ceramic substrates and injection molded lead
frames. It should be noted that an aluminum substrate must be
further attached to the ceramic substrate. Thus, high cost of the
ceramic substrate and addition of the aluminum substrate result in
high fabrication cost. In addition, as shown in FIGS. 6(A) to 6(C),
injection molding technique results in high series thermal
resistance of light emitting device. Accordingly, the light
emitting device can not be used in high power LED package. As
described above in FIGS. 4(A) to 4(C), there also exists the
problem of bad light collecting efficiency.
[0011] Accordingly, there is a need to develop a low thickness LED
package structure which has low series thermal resistance and low
packaging and application cost and can improve light collecting
efficiency.
SUMMARY OF THE INVENTION
[0012] According to the above defects, a primary objective of the
present invention is to provide a thin thickness light emitting
device.
[0013] Another objective of the present invention is to provide a
light emitting device which can reduce the series thermal
resistance.
[0014] A further objective of the present invention is to provide a
light emitting device which can reduce the fabrication cost.
[0015] Still another objective of the present invention is to
provide a light emitting device which can improve the light
collecting efficiency.
[0016] To achieve the above and other objectives, the present
invention discloses a light emitting device, at least comprising: a
light emitting element with at least two electrodes disposed at the
side of the light output surface thereof; and a base member having
a recess and lead portions corresponding to the electrodes, the
light emitting element being mounted on the base member and
received in the recess, wherein the light output surface faces
toward opening of the recess that becomes smaller while approaching
the light output surface, and the electrodes are respectively in
electrical connection with the lead portions that extend from the
connection positions to outer edge of the base member for power
connection.
[0017] Compared with the prior art, the light emitting device of
the present invention achieves a much simpler light emitting device
of thin thickness by combining a light emitting element with a base
member which is connected to the power through lead portions of the
base member, thereby resulting in short current path and low series
thermal resistance and low cost. In addition, the depth of the
recess can be increased to improve the light collecting
efficiency.
BRIEF DESCRIPTION OF DRAWINGS
[0018] FIGS. 1(A) to 1(C) are diagrams illustrating a first light
emitting diode package structure according to the prior art;
[0019] FIGS. 2(A) to 2(C) are diagrams illustrating a second light
emitting diode package structure according to the prior art;
[0020] FIGS. 3(A) to 3(C) are diagrams illustrating a third light
emitting diode package structure according to the prior art;
[0021] FIGS. 4(A) to 4(C) are diagrams illustrating a fourth light
emitting diode package structure according to the prior art;
[0022] FIGS. 5(A) to 5(C) are diagrams illustrating a fifth light
emitting diode package structure according to the prior art;
[0023] FIGS. 6(A) to 6(C) are diagrams illustrating a sixth light
emitting diode package structure according to the prior art;
[0024] FIGS. 7(A) to 7(E) are diagrams illustrating detailed
structure of a light emitting device according to the present
invention;
[0025] FIGS. 8(A) to 8(B) are diagrams illustrating structures of a
light emitting device according to two other embodiments of the
present invention;
[0026] FIGS. 9(A) to 9(B) are diagrams respectively illustrating
structure of a base member having a deeper recess and structure of
a light emitting device comprising such a base member according to
the present invention;
[0027] FIG. 10 is a side sectional view of a light emitting device
according to another embodiment of the present invention;
[0028] FIG. 11 is a plan view of the light emitting device of FIG.
10; and
[0029] FIG. 12 to 14 are plan views illustrating light emitting
devices according to other embodiments of the present
invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0030] Hereunder, embodiments of the present invention will be
described in full detail with reference to the accompanying
drawings.
[0031] FIGS. 7(A) to 7(E) are diagrams showing detailed structure
of a light emitting device according to the present invention. The
light emitting device of the present invention at least includes a
light emitting element 60 (shown in FIG. 7(A)) and a base member 61
(shown in FIG. 7(B)) to which the light emitting element 60 can be
mounted.
[0032] As shown in FIG. 7(A), the light emitting element 60 has at
least two electrodes 600 and 601 disposed at the side of the light
output surface of the light emitting element 60 for power
connection. Preferably, the light emitting element 60 includes at
least one light emitting chip 602 and at least one substrate 603
provided with electrodes 600 and 601 for power connection. The
light emitting chip 602 in a flip chip configuration is mounted to
the substrate 603 and electrically connected with the substrate 603
via gold balls, tin balls or any electrically and thermally
conductive material. Preferably, the substrate 603 is formed of Si,
Al, or C.
[0033] As shown in FIG. 7(B), the base member 61 is a lead frame
formed of PPA resin, PC thermoplastic material or any insulating
material by injection molding or assembly. The base member 61 has a
recess 610 in which the light emitting element 60 can be received
with its light output surface facing toward opening of the recess
610, the opening of the recess 610 becoming smaller while
approaching the light output surface. In addition, two lead
portions 611 and 612 are disposed on the base member 61 to
electrically connect electrodes 600 and 601 of the light emitting
element 60. In the present embodiment, the lead portions 611 and
612 are coated with conductive adhesives 613 and 614 to fix the
electrodes 600 and 601 to the lead portions 611 and 612 and provide
electrical connection between them. Preferably, the conductive
adhesives 613 and 614 are formed of silver paste, solder paste or
solder paste containing lead. The above lead portions and
electrodes can also be fixed and electrically connected via gold
balls or tin balls by using flip chip technology, or through
conductive bonding material by using ultrasonic bonding technology.
The lead portions 611 and 612 extend from the electrically
connecting positions of the light emitting element 60 and the base
member 61 to outer edge of the base member 61 for power connection.
The lead portions are formed of electrically conductive conductor
such as Au, Ag, Cu, Sn, Al or the like.
[0034] As shown in FIG. 7(C), the light emitting element 60 is
attached to the base member 61 in the arrow direction by the
conductive adhesives 613 and 614, thereby forming a structure as
shown in FIG. 7(D). Then, underfill and package processes are
performed to fill the recess 610 with sealing member 617 so as to
fix the light emitting element 60 to the base member 61. The final
structure of the light emitting device is shown in FIG. 7(E). It
should be noted that although the sealing member in FIG. 7(E) forms
a flat plane at the light output surface, it is not limited
thereto. The sealing member can have a lens shape or the like to
improve light collecting efficiency. In addition, as shown in FIG.
8(A), a light reflecting portion 615 can be disposed in the recess
adjacent to the light output surface to reflect the light beam
emitted from the light emitting element 60 to walls of the recess
610, which further reflect the light to form a substantially
collimated light beam to improve the light efficiency. The light
reflecting portion 615 is fixed by the sealing member 617 as
described above. Preferably, the light reflecting portion 615 is
formed of reflective material by electroplating or assembling.
[0035] As shown in FIG. 8(B), a light converting portion 616 is
disposed in the recess adjacent to the light output surface to
change the wavelength of the light emitted from the light emitting
element 60, thereby improving light efficiency. The light
converting portion 616 is fixed by the sealing member 617 as
described above and formed of fluorescent converting material by
coating.
[0036] As shown in FIG. 9(A), since the base member 61a has a thin
thickness, the depth of the recess 610a can be increased to improve
light collecting efficiency. As shown in FIG. 9(B), the light
emitting element 60a is fixed to the base member 61a by underfill
and package. Thus, compared with the prior art, the thickness of
the light emitting device of the present invention becomes much
thinner, thereby reducing the fabrication cost. On the other hand,
even if the light emitting device of the present invention has same
thickness as that of the prior art, the depth of the recess 610a
can be increased to achieve better light collecting efficiency.
[0037] To solve the heat dissipating problem of the light emitting
device, the present invention proposes another embodiment, as shown
in FIG. 10. The surface of the light emitting element 60b opposite
to the light output surface is mounted with a thermal conductor 62
such that the heat generated by the light emitting element 60b can
be dissipated efficiently when the light emitting element 60b is
connected to the power. In FIG. 10, printed circuit board 70 is
used to supply power. Preferably, the thermal conductor 62 of a
plate shape is formed of Al, Cu, Fe or material having a thermal
conductivity of at least 50 W/mK. Furthermore, an adhesive layer 63
can be disposed between the thermal conductor 62 and the light
emitting element 60b to fix the light emitting element 60b to the
surface of the thermal conductor 62. Preferably, the adhesive layer
63 is formed of heat sink paste. Thus, by separating the thermally
conductive structure from the electrically conductive structure,
the present invention decreases the conductive path, thereby
decreasing series thermal resistance and increasing reliability of
products.
[0038] FIG. 11 is a plan view of the light emitting device in FIG.
10. As shown in FIG. 11, the light emitting element 60b comprises a
single chip emitting single color. However, the light emitting
element 60b is not limited thereto. As shown in FIG. 12, the light
emitting element 60b could be composed of multiple chips, which
outputs single color by light mixing. Alternatively, as shown in
FIGS. 13 and 14, light emitting elements 60c and 60d respectively
include multiple chips which emit light alternately to output
multi-color light source for application. In addition, the light
element could emit ultraviolet.
[0039] Therefore, the light emitting device of the present
invention at least includes a light emitting element having at
least two electrodes located at the side of the light output
surface thereof and a base member to which the light emitting
element can be mounted. Therein, the light emitting element is
received in a recess of the base member with its light output
surface facing toward the opening of the recess that gradually
decreases while approaching the light output surface and the
electrodes of the light emitting elements are electrically
connected with lead portions of the base member that extend toward
the outer edge of the base member for power connection. As a
result, the present invention achieves a light emitting device of
thin thickness, which accordingly has advantages of short current
path, low series thermal resistance and low cost. In addition, the
depth of the recess can be increased to improve light collecting
efficiency, which is not limited to the depth of 6 mm as in the
prior art. Further, compared with the prior art that only can mount
the light emitting element from the front side of the base member,
since a hollow base member is used in the present invention, the
light emitting element can be mounted into the recess from the back
side of the base member, thereby facilitating the mounting
process.
[0040] The invention has been described using exemplary preferred
embodiments. However, it is to be understood that the scope of the
invention is not limited to the disclosed embodiments. On the
contrary, it is intended to cover various modifications and similar
arrangements. The scope of the claims, therefore, should be
accorded the broadest interpretation so as to encompass all such
modifications and similar arrangements.
* * * * *