U.S. patent application number 12/572974 was filed with the patent office on 2010-01-28 for led of side view type and the method for manufacturing the same.
This patent application is currently assigned to ALTI-ELECTRONICS CO., LTD.. Invention is credited to Chi-Ok In, Sun-Hong Kim, Jin-Won Lee, Ik-Seong PARK.
Application Number | 20100019267 12/572974 |
Document ID | / |
Family ID | 37621705 |
Filed Date | 2010-01-28 |
United States Patent
Application |
20100019267 |
Kind Code |
A1 |
PARK; Ik-Seong ; et
al. |
January 28, 2010 |
LED OF SIDE VIEW TYPE AND THE METHOD FOR MANUFACTURING THE SAME
Abstract
A side view type light emitting diode (LED) and a method of
manufacturing the same are disclosed. In one embodiment, the LED
includes i) a pair of lead frames, ii) a reflector surrounding the
lead frames, wherein a groove is defined in the reflector, wherein
the reflector comprises a plurality of walls surrounding the
groove, and wherein at least two walls of the groove face each
other, iii) an LED chip mounted in the groove and electrically
connected to the lead frames and iv) a lens array contained in the
groove.
Inventors: |
PARK; Ik-Seong; (Seoul,
KR) ; Lee; Jin-Won; (Yongin-si, KR) ; In;
Chi-Ok; (Dangjin-gun, KR) ; Kim; Sun-Hong;
(Incheon, KR) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Assignee: |
ALTI-ELECTRONICS CO., LTD.
Yongin-si
KR
|
Family ID: |
37621705 |
Appl. No.: |
12/572974 |
Filed: |
October 2, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11906869 |
Oct 4, 2007 |
7598101 |
|
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12572974 |
|
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|
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PCT/KR2006/004447 |
Oct 30, 2006 |
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11906869 |
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Current U.S.
Class: |
257/98 ; 257/99;
257/E33.056; 257/E33.066; 257/E33.067 |
Current CPC
Class: |
H01L 2224/45015
20130101; H01L 2224/73265 20130101; G02B 6/0068 20130101; G02B
6/0065 20130101; H01L 24/45 20130101; H01L 2924/181 20130101; H01L
33/62 20130101; G02B 6/0083 20130101; G02B 6/0091 20130101; H01L
33/486 20130101; G02B 6/0073 20130101; H01L 2224/48091 20130101;
H01L 2224/45144 20130101; H01L 2224/48247 20130101; H01L 24/73
20130101; H01L 2924/181 20130101; H01L 2224/45144 20130101; H01L
2224/48091 20130101; H01L 2924/00012 20130101; H01L 2924/00
20130101; H01L 2224/32245 20130101; H01L 2924/00012 20130101; H01L
2924/20752 20130101; H01L 2224/48247 20130101; H01L 2924/00014
20130101; H01L 2224/32245 20130101; H01L 2924/00012 20130101; H01L
2924/12041 20130101; G02B 6/0031 20130101; H01L 2224/45015
20130101; H01L 33/60 20130101; H01L 2224/73265 20130101; H01L
2924/12041 20130101 |
Class at
Publication: |
257/98 ; 257/99;
257/E33.066; 257/E33.056; 257/E33.067 |
International
Class: |
H01L 33/00 20060101
H01L033/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 9, 2005 |
KR |
10-2005-0106916 |
Claims
1. A side view type light emitting diode (LED) comprising: a pair
of lead frames; a reflector surrounding the lead frames, wherein a
groove is defined in the reflector, wherein the reflector comprises
a plurality of walls surrounding the groove, and wherein at least
two walls of the groove face each other; an LED chip mounted in the
groove and electrically connected to the lead frames; and a lens
array contained in the groove.
2. The side view type light emitting diode of claim 1, wherein the
walls of the groove facing each other have thicknesses of about
0.04 mm to about 0.05 mm at the upper surfaces.
3. The side view type light emitting diode of claim 1, wherein the
pair of lead frames have the form of a strip, and wherein the lead
frames facing each other are arranged in a straight type
configuration and separated by a predefined gap, and have portions
thereof protruding out of the reflector.
4. The side view type light emitting diode of claim 3, wherein the
protruding portions have a tapered shape such that the width
becomes narrower towards the end.
5. The side view type light emitting diode of claim 1, wherein the
height of the walls is about 0.25 mm to about 0.35 mm.
6. The side view type light emitting diode of claim 1, wherein the
reflector comprises a plastic material.
7. The side view type light emitting diode of claim 6, wherein the
width of the groove is about 0.3 mm to about 0.35 mm.
8. The side view type light emitting diode of claim 1, wherein an
inner surface of the wall is inclined with respect to a bottom
surface of the groove.
9. The side view type light emitting diode of claim 1, wherein the
pair of lead frames have the form of a strip, and wherein the lead
frames facing each other are arranged in a straight type
configuration and separated by a predefined gap, and have portions
thereof protruding out of the reflector.
10. The side view type light emitting diode of claim 9, wherein the
protruding portions have a tapered shape such that the width
becomes narrower towards the end.
Description
RELATED APPLICATIONS
[0001] This application claims priority to and is a divisional
application of U.S. application Ser. No. 11/906,869, filed Oct. 4,
2007, which is a continuation application, and claims the benefit
under 35 U.S.C. .sctn..sctn.120 and 365 of PCT Application No.
PCT/KR2006/004447, filed on Oct. 30, 2006, both of which are hereby
incorporated by reference. PCT/KR2006/004447 also claimed the
priority of Korean Patent Application No. 10-2005-0106916, filed on
Nov. 9, 2005, in the Korean Intellectual Property Office, which is
hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a light emitting diode,
more particularly to a side view type light emitting diode and a
method of manufacturing the same.
SUMMARY OF CERTAIN INVENTIVE ASPECTS
[0003] An aspect of the present invention provides a side view type
light emitting diode and a method of manufacturing the same, in
which, with a low cost, the thicknesses of the walls are made to be
about 0.04 mm to about 0.05 mm for an overall thickness of about
0.5 mm or lower, according to the trend of the thickness of the
light guide plate in a backlight device decreasing to about 0.5 mm
or lower.
[0004] Another aspect of the present invention provides a side view
type light emitting diode and a method of manufacturing the same,
in which the manufacturing process is simplified by forming
straight type electrodes without additional processes of folding or
bending, etc., when forming the lead frames, and in which the
electrical contact between the lead frames and the conductive
pattern on the PCB and the supply of electricity are made more
efficient by providing cutting-grooves on the lead frames (at the
ends of the lead frames), when mounting the side view type light
emitting diode on the PCB.
[0005] Another aspect of the present invention provides a side view
type light emitting diode and a method of manufacturing the same,
in which the height of the walls forming the reflectors is
minimized, so that the total quantity of light emitted is
increased, and the occurrence of dark spots is minimized when
fitting onto a backlight device of an LCD. Another aspect of the
present invention provides a method of manufacturing a side view
type light emitting diode comprising: (a) providing lead frames
which include a cathode terminal and an anode terminal, (b) forming
a reflector which surrounds the lead frames, such that portions of
the cathode terminal and anode terminal protrude from both sides,
and which includes a groove open in the upward direction and a wall
surrounding the groove, (c) die-attaching an LED chip onto the lead
frames inside the groove, (d) bonding the LED chip to the cathode
terminal or to the anode terminal with a conductive wire, (e)
dispensing a liquid curable resin into the groove to form a lens
part and (f) sawing the walls facing each other using a sawing
machine, such that the thicknesses at the upper surfaces are about
0.04 mm to about 0.05 mm.
[0006] Here, the lead frames may be formed by punching a copper
(Cu) board plated with silver (Ag) using a press cast, and may
include cutting-grooves on both side portions of the outer ends of
the cathode terminal and the anode terminal.
[0007] Meanwhile, the reflector may be formed by plastic injection
molding such that the width of the groove is about 0.3 mm to about
0.35 mm. Also, the inner surface of the wall may be formed to have
a predefined inclination with respect to the bottom surface.
[0008] Any one of the (b) forming, the (c) die-attaching, and the
(d) bonding may further include coating a reflective substance or
joining a reflective plate of a metal material on the inner surface
of the wall.
[0009] The liquid curable resin may include liquid epoxy with a
fluorescent substance mixed in, which may be in correspondence with
the color of the LED chip.
[0010] Another aspect of the present invention provides a side view
type light emitting diode comprising: a pair of lead frames; a
reflector which surrounds the lead frames and which includes a
groove that is open in an upward direction and a wall that
surrounds the groove; an LED chip mounted in the groove and
electrically connected by wire bonding to the lead frame; and a
lens part filled in the groove, where the walls facing each other
have thicknesses of about 0.04 mm to about 0.05 mm at the upper
surfaces.
[0011] The pair of lead frames may be in the form of a strip, and
the lead frames facing each other may be arranged in a straight
type configuration and separated by a predefined gap, and may have
portions protruding out of the reflector. Here, the portions
protruding out of the reflector may have a tapered shape, such that
the width is narrower towards the end. Also, the height of the wall
may be about 0.25 mm to about 0.35 mm.
[0012] Still another aspect of the present invention provides a
side view type light emitting diode comprising: a pair of lead
frames; a reflector which surrounds the lead frames and which
includes a groove that is open in an upward direction and a wall
that surrounds the groove; an LED chip mounted in the groove and
electrically connected by wire bonding to the lead frame; and a
lens part filled in the groove, where the height of the wall is
about 0.25 mm to about 0.35 mm. The reflector may include a plastic
material, the side view type light emitting diode may be formed by
injection molding, and the inner surface of the wall may be formed
to have a predefined inclination with respect to the bottom surface
of the groove.
[0013] The lens part may be formed by curing liquid epoxy that
includes a fluorescent substance in correspondence with the color
of the light emitted by the LED chip.
[0014] Also, the pair of lead frames may be in the form of a strip,
and the lead frames facing each other may be arranged in a straight
type configuration and separated by a predefined gap, and may have
portions protruding out of the reflector. Here, the portions
protruding out of the reflector may have a tapered shape, such that
the width is narrower towards the end.
[0015] Still another aspect of the invention provides a method of
manufacturing a side view type light emitting diode (LED), the
method comprising: (a) providing lead frames comprising a cathode
terminal and an anode terminal, (b) forming a reflector surrounding
the lead frames such that portions of the cathode terminal and
anode terminal protrude from both sides of the reflector, wherein a
groove is defined in the reflector, wherein the reflector comprises
a plurality of walls surrounding the groove, and wherein at least
two walls of the groove face each other, (c) die-attaching an LED
chip on the lead frames inside the groove, (d) bonding the LED chip
to the cathode terminal or the anode terminal with a conductive
wire, (e) dispensing a liquid curable resin into the groove to form
a lens array and (f) sawing the walls of the groove facing each
other using a sawing machine.
[0016] Yet another aspect of the invention provides a side view
type light emitting diode (LED) comprising: i) a pair of lead
frames, ii) a reflector surrounding the lead frames, wherein a
groove is defined in the reflector, wherein the reflector comprises
a plurality of walls surrounding the groove, and wherein at least
two walls of the groove face each other, iii) an LED chip mounted
in the groove and electrically connected to the lead frames and iv)
a lens array contained in the groove.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a cross-sectional view for a typical LED applied
to an LCD backlight device.
[0018] FIG. 2 is a front-elevational view illustrating an example
of a typical LED.
[0019] FIG. 3 is a cross-sectional view for describing another
problem in a typical LED applied to an LCD backlight device.
[0020] FIG. 4 is a plan view of a typical side view type light
emitting diode arrayed in an LCD backlight device.
[0021] FIG. 5 is a flowchart schematically representing a method of
manufacturing a side view type light emitting diode according to an
embodiment of the present invention.
[0022] FIG. 6 is a plan view illustrating lead frames according to
an embodiment of the present invention.
[0023] FIG. 7 is a plan view illustrating the lead frames of FIG. 6
after forming a reflector on the lead frames.
[0024] FIG. 8 is a cross-sectional view across line A-A' of FIG.
7.
[0025] FIG. 9 is a cross-sectional view across line B-B' of FIG.
7.
[0026] FIG. 10 is a cross-sectional view after mounting an LED chip
and performing wire bonding.
[0027] FIG. 11 is a perspective view illustrating a side view type
light emitting diode manufactured according to an embodiment of the
present invention.
[0028] FIG. 12 is a perspective view of a side view type light
emitting diode according to an embodiment of the present
invention.
[0029] FIG. 13 is a cross-sectional view across line C-C' of FIG.
12 for describing the arrangement of the lead frames.
[0030] FIG. 14 is a cross-sectional view across line D-D' of FIG.
12 with the walls of the reflector at a common height h.sub.1.
[0031] FIG. 15 is a cross-sectional view across line D-D' of FIG.
12 with the walls of the reflector at an advantageous height
h.sub.2.
[0032] FIG. 16 is a cross-sectional view across line E-E' of FIG.
12.
[0033] FIG. 17 is a perspective view illustrating an example of the
side view type light emitting diode of FIG. 12 applied to an LCD
backlight device.
[0034] FIG. 18 is a plan view of FIG. 17.
DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS
[0035] With reference to FIGS. 1 and 2, the composition of a
backlight device in a liquid crystal display (LCD) in a mobile
communication equipment is typically as illustrated in FIG. 1. That
is, in a backlight device 10, a flat light guide plate 14 is
arranged on the board, and side light emitting diodes, i.e., LED's
20, are arranged at the sides of this light guide plate 14.
Typically, a plurality of LED's 20 are arranged in the form of
arrays. The light L from the LED's 20 incident on the light guide
plate 14 is reflected upwards by means of minute reflective
patterns or a reflective sheet 16 arranged at the bottom surface of
the light guide plate 14, and is emitted from the light guide plate
14 to provide a backlight for the LCD panel 18 above the light
guide plate 14.
[0036] FIG. 2 is a front view showing an example of a typical LED
20 such as that illustrated in FIG. 1. Referring to FIG. 2, an LED
20 includes a cup-shaped groove 28 housing an LED chip 22 (see FIG.
1) within, and a package body 23 having thin walls 24 at the top
and bottom and relatively thick walls 26 to the left and right of
the groove 28. In order to guide the light generated at the LED
chip 22 to the exterior, the cup-shaped groove 28 is open towards
the front of the drawing to form an LED window, which is filled
with a transparent resin to seal the LED chip from the exterior.
Here, a fluorescent element, etc., may be included in the resin for
converting a single color light into white light. Also, a pair of
terminals 29 are installed on both sides of the package body 23 to
electrically connect the LED chip 22 to an exterior power
source.
[0037] With this composition, the terminals 29 are not superposed
with the groove 28, so that the overall thickness of the LED 20 is
reduced.
[0038] In particular, there is currently a demand for the reduction
of thickness in LCD backlight devices, and a thickness reduction in
the LED's is advantageous for the thickness reduction in backlight
devices. At present, there is a demand for a thickness of about 0.6
mm or lower for side view type light emitting diodes (LED's) in LCD
backlight devices, and it is expected that the demand will be for
thicknesses of about 0.5 mm or lower in the future.
[0039] However, with the LED 20 having a structure such as that
illustrated in FIGS. 1 and 2, it is difficult to ensure a package
thickness, i.e., fitted height, of 0.5 mm or lower. This is because
the opening of the groove 28, i.e., the LED window, requires a
certain amount of width for guiding the light generated at the LED
chip 22 to the exterior, the walls 24 at the top and bottom of the
LED window also require a certain amount of thickness to ensure a
desired strength, and it is difficult to make this thickness go
below a certain amount with only the injection-molding type of
manufacturing method.
[0040] Another problem in the typical LED applied to LCD backlight
devices is that the opening of the groove 28, i.e., the LED window
is separated upwards by a thickness t.sub.h of the lower wall 24
from the bottom of the light guide plate 14. Thus, the light L
generated at the LED chip 22 and emitted downwards towards the
exterior of the groove 28 proceeds along a predetermined length
before reaching the reflective sheet 16 at the bottom of the light
guide plate 14. This creates first dark spots 33, in which the
light L is dim, on the reflective sheet 16, to degrade the overall
efficiency of the LCD backlight device.
[0041] Meanwhile, with the miniaturization of mobile communication
equipment on which the LCD backlight device is equipped, there is
also a trend of reducing the thickness of the light guide plate for
the LCD backlight device. That is, the thickness of the light guide
plate is being reduced to about 0.5 mm and lower.
[0042] In this case, another problem occurs in the LCD backlight
device that employs typical LED's, as described below with
reference to FIG. 3. As illustrated in FIG. 3, when the thickness
of the light guide plate 14a is about 0.5 mm or lower, the
thickness of the LED's 20a is made greater than that of the light
guide plate 14a. Then, a substantial amount of light generated at
the LED chip 22a within the LED 20a does not reach the light guide
plate 14a, and light loss occurs. Thus, to prevent this problem, an
LCD backlight device 10a has reflectors 35 installed at the upper
ends of the sides of the light guide plate 14a to guide the light
to the inside of the light guide plate 14a and prevent light
loss.
[0043] However, this further complicates the composition of the LCD
backlight device 10a, as well as its manufacturing process, which
in turn increases the work times and costs.
[0044] Moreover, as illustrated in FIG. 4, there are a plurality of
side view type light emitting diodes, i.e., LED's 20, arranged in
the form of arrays on the board 12 at the sides of the light guide
plate 14, where second dark spots 36, in which the light generated
at the LED chips 22 are dim, exist between the plurality of LED's
20, to also degrade the overall efficiency of the LCD backlight
device.
[0045] Furthermore, as the depth of the groove 28 of the LED 20
(i.e., the distance from the surface of the terminal 29 on which
the LED chip 22 is mounted to the upper surface of the wall 24) is
typically about 0.6 mm or greater, the number of times the light
emitted from LED chip 22 is reflected between the inner surfaces of
the walls 24 is high, so that light loss is increased.
[0046] Embodiments of the side view type light emitting diode and a
method of manufacturing the same will be described below in more
detail with reference to the accompanying drawings. In the
description with reference to the accompanying drawings, those
components are rendered the same reference number that are the same
or are in correspondence regardless of the figure number, and
redundant explanations are omitted.
[0047] FIG. 5 is a flowchart schematically representing a method of
manufacturing a side view type light emitting diode according to an
embodiment of the present invention. In describing the method of
manufacturing a side view type light emitting diode, the respective
operations will be described with reference to FIGS. 6 to 11.
[0048] FIG. 6 is a plan view illustrating lead frames according to
an embodiment of the present invention, FIG. 7 is a plan view
illustrating the lead frames of FIG. 6 after forming a reflector on
the lead frames, FIG. 8 is a cross-sectional view across line A-A'
of FIG. 7, FIG. 9 is a cross-sectional view across line B-B' of
FIG. 7, FIG. 10 is a cross-sectional view after mounting an LED
chip and performing wire bonding, and FIG. 11 is a perspective view
illustrating a side view type light emitting diode manufactured
according to an embodiment of the present invention.
[0049] First, lead frames 110 (see FIG. 6) are prepared (S1). In
this embodiment, a lead frame plate 110 such as that in FIG. 6 is
formed by punching a copper (Cu) board plated with silver (Ag)
using a press cast. Here, it is given a thickness of about 0.2 mm,
so that it can release the heat generated in the LED chip to the
exterior.
[0050] A pair of lead frames 111 in the form of a strip is arranged
such that the ends on the inside facing each other are separated by
a predefined gap G, and the ends on the outside are connected on
both sides by connection pieces 113. One side of the pair of lead
frames 111 becomes the cathode terminal 111a, while the other side
becomes the anode terminal 111b.
[0051] Meanwhile, cutting-grooves 115 are formed on the outer parts
of the portions where the outer ends of the lead frames meet the
connection pieces. The function of the cutting-grooves 115 will be
described later.
[0052] Second, a reflector 120 (see FIGS. 7 to 9) is formed on the
lead frame plate 110 (S2).
[0053] A reflector 120 is formed, which surrounds the pair of lead
frames 111 such that the ends protrude out at both the left and
right sides, and which has a cup-shaped elongated groove 125 that
houses the LED chip 130 (see FIG. 10) within, and thin upper and
lower walls 121a, 121b and relatively thick left and right walls
123a, 123b surrounding it. The reflector 120 is formed on the upper
and lower parts of the pair of lead frames 111, and is formed by a
general plastic injection molding technique.
[0054] In this embodiment, the upper and lower thin walls 121a,
121b are made with a thickness of about 0.2 mm each, with the
distance between the inner surfaces of the upper and lower thin
walls 121a, 121b being about 0.3 mm (the thickness of the bottom
surface on which the LED chip is placed) at the bottom of the
groove 125.
[0055] However, with plastic injection molding, the thickness
cannot be made under about 0.07 mm for the walls, especially the
thin walls at the top and bottom, and the manufacturing cost is
increased the more the thickness is decreased, and even if the
reflector is manufactured at a high cost with about 0.07 mm for the
thickness of the walls, there are still problems remaining, in that
the overall thickness of the side view type light emitting diode is
made greater than about 0.5 mm, to be unable to satisfy the trends
for a light guide plate 14a (see FIG. 3) having a thickness of
about 0.5 mm or lower, and that reflectors 35 (see FIG. 3) may have
to be used. A technical solution to these problems is achieved by
the final operation of the method of manufacturing a side view type
light emitting diode according to one embodiment of the present
invention, the sawing of the lead frames and walls (S6, see FIG.
5). Detailed descriptions on this will be provided later.
[0056] Meanwhile, in consideration of the light emission efficiency
of the side view type light emitting diode, the inner surfaces of
the walls 121a, 121b, 121a, 121b are formed to have inclinations,
while reflective substances may be coated on or a reflective plate
of a metal material may be joined to the inner surfaces of the
walls 121a, 121b, 121a, 121b.
[0057] Third, the LED CHIP 130 (see FIG. 9) is die-attached (S3).
In this embodiment, the LED chip 130 is attached onto the lead
frame 111a inside the groove 125 using conductive paste 133, and an
LED chip 130 of dimensions about 0.24 mm.times.about 0.48
mm.times.about 0.1 mm is used.
[0058] Fourth, the LED chip 130 is bonded to the lead frame 111b
with a conductive wire 135 (see FIG. 10) (S4). In this embodiment,
a gold (Au) wire 135 was used.
[0059] While in this embodiment, the LED chip 130 is attached to
the lead frame 1a of one side by means of conductive paste 133 and
bonded afterwards to the lead frame 111b of the other side with a
gold (Au) wire 135 for electrical connection, the case may also be
considered in which the LED chip is attached onto the mold of the
reflector 120 between the opposing ends at the insides of the pair
of lead frames 111a, 111b by means of non-conductive paste (not
shown), with wire bonding respectively to the lead frames 111a,
111b of both sides.
[0060] Fifth, a lens part is formed in the groove 125 of the
reflector (S5). The lens part 137 is formed by dispensing liquid
epoxy, mixed with a fluorescent substance in correspondence with
the color of the LED chip 130, in the groove 125.
[0061] Meanwhile, while in this embodiment, the lens part 137 was
formed by mixing a fluorescent substance in liquid epoxy, the case
may also be considered in which the lens part 137 is formed by
potting the fluorescent substance on the LED chip 130 and
afterwards injecting a curable resin such as liquid epoxy into the
groove 125 of the reflector.
[0062] Finally, the lead frame plate and the walls are sawed (S6).
Using a sawing machine that utilizes blades, both of the walls
121a, 121b facing each other are sawed along cutting lines C (see
FIGS. 7 and 8) such that the thickness of each at the upper surface
is about 0.04 mm, whereby the side view type light emitting diode
100 and the method of manufacturing the same are completed.
[0063] As described above, it is difficult to make the thicknesses
of the walls be about 0.07 mm or lower with injection molding, so
that in this embodiment, a sawing machine utilizing blades is used
to make the thicknesses t.sub.2 of the walls 121a, 121b be about
0.04 mm each and to make the top width t.sub.3 of the groove of the
reflector be about 0.32 mm, whereby the overall thickness t (see
FIG. 11) of the side view type light emitting diode is made about
0.4 mm.
[0064] By thus radically reducing the overall thickness of the side
view type light emitting diode without incurring high costs, the
thickness of the LCD backlight device employing the side view type
light emitting diode may be reduced, to satisfy the trends of using
light guide plates of about 0.5 mm or lower.
[0065] Moreover, by reducing the thicknesses t.sub.2 of the walls
121a, 121b to about 0.4 mm each, the first dark spots 33 (see FIG.
1) may be minimized, to increase light emission efficiency when
applying a side view type light emitting diode based on one
embodiment the present invention to an LCD backlight device.
[0066] Meanwhile, when the lead frames 110 (see FIG. 7) and the
reflector 120 are sawed along the cutting lines C, the
cutting-grooves 115 give the pair of lead frames 111a, 111b a
tapered shape such that the width is narrower towards the end,
whereby the ends may be formed without sawing.
[0067] Thus, the problem in using a copper (Cu) board plated with
silver (Ag), of having the plated silver (Ag) detached from the
copper (Cu) board during sawing, such that the efficiency is
degraded in electrical contact between the lead frames and the
conductive patterns on the PCB and in the supply of electricity
when mounting the side view type light emitting diode on the PCB,
is resolved for the lead frames.
[0068] FIG. 12 is a perspective view of a side view type light
emitting diode according to an embodiment of the present invention,
FIG. 13 is a cross-sectional view across line C-C' of FIG. 12 for
describing the arrangement of the lead frames, FIG. 14 is a
cross-sectional view across line D-D' of FIG. 12 with the walls of
the reflector at a common height h.sub.1, FIG. 15 is a
cross-sectional view across line D-D' of FIG. 12 with the walls of
the reflector at an advantageous height h.sub.2, and FIG. 16 is a
cross-sectional view across line E-E' of FIG. 12.
[0069] Referring to FIGS. 12 and 13, a reflector 120' is comprised,
which surrounds the pair of lead frames 111', such that an end
portion protrudes on both sides, and which includes a cup-shaped
groove housing the LED chip 130' (see FIGS. 14 to 16) within, and
thin walls 121'a, 121'b at the top and bottom and relatively thick
walls 123'a, 123'b to the left and right of the groove 125'
surrounding it. The reflector 120' is formed at the upper and lower
portions of the pair of lead frames 111', and is typically formed
by a general plastic injection molding technique.
[0070] As shown in FIG. 13, the pair of lead frames 111' in the
form of a strip have the ends facing each other separated by a
predefined gap, and are arranged in a straight type configuration,
without any folded or bent surfaces overall. One side of the pair
of lead frames 111' becomes the cathode terminal 111'a, while the
other side becomes the anode terminal 111'b. The polarity of each
terminal may be changed as necessary.
[0071] Also, in order for the plastic mold forming the reflector
120' to surround the lead frames 111' and be vertically connected,
such that the lead frames 111' are stably supported, a portion of
the inner sides of the lead frames 111' is made to have a narrower
width than that of either outer end.
[0072] The pair of lead frames 111' used in this embodiment are
formed by punching a copper (Cu) board plated with silver (Ag)
using a press cast, where the lead frames 111' have a thickness of
about 0.2 mm, so that they can emit the heat generated in the LED
chip to the exterior of the side view type light emitting
diode.
[0073] Also, each outer end of the pair of lead frames 111'a, 111'b
may have a tapered shape, such that the width is narrower towards
the end.
[0074] This is because, this shape may solve the problem of the
plated silver (Ag) becoming detached from the copper (Cu) board,
when manufacturing the pair of lead frames 111'a, 111'b by sawing
the lead frame plate made of a copper (Cu) board plated with silver
(Ag); it may increase the efficiency of electrical contact with the
conductive patterns on the PCB, by providing room for the solder
between the PCB and the ends of the lead frames, when mounting a
side view type light emitting diode 100' based on one embodiment of
the present invention on the PCB; and it may improve the
heat-releasing effect through the lead frames, by allowing the side
view type light emitting diode to closely adhere to the PCB.
[0075] Referring to FIG. 16, the LED 130' (about 0.24
mm.times.about 0.48 mm.times.about 0.1 mm) is mounted on the lead
frame 111'a of one side exposed through the inside of the groove
125' of the chip reflector 120', where the LED chip 130' is
attached by means of conductive paste 133' and is bonded with the
lead frame 111'b of the other side by a gold (Au) wire 135' to be
electrically connected.
[0076] Also, instead of attaching the LED chip 130' onto the lead
frame 111'a of one side by means of conductive paste 133' and
afterwards bonding to the lead frame 111'b of the other side by
means of a gold (Au) wire 135', the case may also be considered in
which the LED chip is attached onto the lead frame 111'a of one
side by means of non-conductive paste (not shown) and then
performing wire bonding respectively with the lead frames 111'a,
111'b of both sides.
[0077] Meanwhile, a lens part 137' is comprised in the groove 125'
of the reflector which protects the LED chip 130' and the gold (Au)
wire 135'. In this embodiment, the lens part 137' is formed by
dispensing a liquid epoxy mixed with a fluorescent substance in
correspondence with the color of the LED chip 130'. By means of the
fluorescent substance, a single color light may be implemented
using an LED chip 130' that emits a single color light.
[0078] Meanwhile, while in this embodiment the lens part 137' was
formed by mixing a fluorescent substance in liquid epoxy, the case
may also be considered in which the lens part 137' is formed by
potting the fluorescent substance on the LED chip 130' and
afterwards injecting a curable resin such as liquid epoxy into the
groove 125' of the reflector.
[0079] With reference to FIGS. 14 to 18, the following describes
why the light emission efficiency and total light quantity are
improved for the case of using an advantageous height h.sub.2 for
the walls of the reflector according to an embodiment of the
present invention, in comparison to the case of using a common
height h.sub.1 for the walls of the reflector.
[0080] FIG. 14 shows the reflection properties of light emitted
from an LED chip 130' when the height of the walls 121' confining
the groove 125' of the reflector is set to about 0.6 mm
(h.sub.1).
[0081] The width t.sub.2' within the groove 125' is set to about
0.3 mm in consideration of the width of the LED chip 130', and the
thickness t.sub.1' at the upper portion of the walls 121' is set to
about 0.1 mm in consideration of structural stability and
injection-molding type manufacture. Here, the inner surfaces of the
walls 121' are given inclinations for reflecting light, the
inclination angle of which is .theta..sub.1.
[0082] Here, the light L.sub.1 emitted from the LED chip 130'
reflects off the inner surfaces of the walls 121' four times, where
the reflections cause the light particles to lose certain amounts
of energy due to the collisions with the inner surfaces of the
walls 121'.
[0083] FIG. 15 shows the reflection properties of light emitted
from an LED chip 130' when the height of the walls 121' confining
the groove 125' of the reflector is set to about 0.3 mm
(h.sub.2).
[0084] When the thickness of the chip is set to a typical value of
about 0.1 mm, the height of the gold (Au) wire 135' (see FIG. 16)
electrically bonding the LED chip 130' and the lead frames 111'
typically becomes about 0.15 mm to about 0.2 mm, and since a range
of about 0.25 mm to about 0.35 mm is advantageous for the height of
the lens part to encapsulate these for protection, and in
consideration of structural stability, the height of the walls 121'
is set to about 0.3 mm (h.sub.2).
[0085] Here, under the condition that t.sub.1', t.sub.2', and t'
are made equal, as in FIG. 14, the inclination angle of the inner
surfaces of the walls becomes .theta..sub.2, where .theta..sub.2 is
greater than .theta..sub.1. According to such increase of
.theta..sub.2, the reflection properties of the light emitted from
the LED chip 130' are also changed.
[0086] That is, the number of reflections of the light L.sub.2
emitted from the LED chip 130' on the inner surfaces of the walls
121' is reduced from four (the number of reflections of L.sub.1,
see FIG. 14) to one, and at the same time, the energy lost due to
the collisions of light particles with the inner surfaces of the
walls 121' when a reflection occurs is also reduced, whereby the
total quantity of light outputted from the side view type light
emitting diode 100' according to one embodiment of the present
invention is improved.
[0087] Considering the recent trends characterized by demands for
the thickness of the light guide plate to be about 0.5 mm or lower,
and under the conditions that decreasing t.sub.1 presents problems
in manufacturing method and cost and decreasing t.sub.2 is limited
by the size of the LED chip, this embodiment increases the
inclination angle of the inner surfaces of the walls by reducing
the height of the walls confining the groove of the reflector to up
to about 0.3 mm, whereby the total quantity of light outputted from
the side view type light emitting diode is effectively
improved.
[0088] FIG. 16 is a cross-sectional view across line E-E' of FIG.
12, where, in order to compare the difference in effect between the
case of using a common height of about 0.6 mm (h.sub.1), according
to prior art, and the case of using an advantageous height of about
0.3 mm (h.sub.2), according to an aspect of the present invention,
for the height of the walls 123'a, 123'b, the former case is
illustrated by dotted lines.
[0089] As shown in FIG. 16, as the height of the walls 123'a, 123'b
is reduced from about 0.6 mm (h.sub.1) to about 0.3 mm (h.sub.2),
under the condition that the thickness t.sub.3' of the upper
surface of the walls 123'a, 123'b is kept constant, it is seen that
.theta.v (view angle), which represents the angle of the light
emitted to the sides, is increased from .theta.v.sub.1 to
.theta.v.sub.2.
[0090] FIG. 17 is a perspective view illustrating an example of the
side view type light emitting diode 100' of FIG. 12 applied to an
LCD backlight device, and FIG. 18 is a plan view of FIG. 17.
[0091] Referring to FIGS. 17 and 18, a plurality of side view type
light emitting diodes 100' are arranged in the form of arrays on a
board 112 adjacent to a side of the light guide plate 114.
[0092] Here, according to an aspect of the present invention,
.theta.v (view angle) is increased as in FIG. 16, as described
above, and as the area of the dark spots 136 that appear on the
light guide plate 114 in-between the plurality of side view type
light emitting diodes 100' is reduced compared to the second dark
spots (see FIG. 4) of when typical side view type light emitting
diodes are fitted, the problem in prior art of decreased overall
efficiency of the LCD backlight device is resolved.
[0093] An example comparison experiment is described below with
reference to FIGS. 14 and 15. The overall thickness t' of the side
view type light emitting diode used in the experiment is about
0.425 mm, the width t.sub.2' of the bottom surface of the groove on
which the LED chip 130' is placed is about 0.3 mm, a blue chip of
dimensions about 0.24 mm.times.about 0.48 mm.times.about 0.1 mm is
used for the LED chip 130', a clear type (D-20-4) die-attaching
paste is used to bond with the lead frame 111'b of one side by
means of a 1 mil standard gold (Au) wire 135', and the lens part
137' was implemented to output white light by dispensing a
fluorescent substance (about 30%) mixed in a liquid epoxy (YE 1205
A/B epoxy) from YESMTECH company. Also, the delivered voltage was
about 20 mA per LED chip 130'.
[0094] The CAS 140B from the Instrument company of Germany,
currently often used in the LED industry as an initialization (data
calibration) instrument, was used for the measurement instrument,
and the measurement position was set to about 100 mm from the LED
chip 130'.
[0095] Under the above conditions, the luminances of light were
compared between the cases of setting the height of the walls 121'
confining the groove 125' of the reflector to be about 0.57 mm (a)
and about 0.3 mm (b).
[0096] The results of the comparison experiment, as seen in Table
1, is that the total quantity of light emitted (i.e. luminance) is
increased by about 10% for the side view type light emitting diode
in which the height of the wall 121' is about 0.3 mm, compared to
the case where the height is about 0.57 mm.
TABLE-US-00001 TABLE 1 <Luminance Comparison Experiment Data
According to Wall Height> (a) Height of Wall 121 (b) Height of
Wall 121 set to 0.57 mm set to 0.3 mm Luminance Wavelength
Luminance Wavelength No. (mcd) (nm) (mcd) (nm) 1 1.05 456.83 1.17
455.67 2 1.08 456.25 1.14 455.75 3 1.07 455.18 1.19 454.27 4 1.07
454.66 1.19 454.50 5 1.07 455.07 6 1.06 455.80 Min. 1.05 454.66
1.14 454.27 Max. 1.08 456.83 1.19 454.75 Avg. 1.07 456.63 1.17
455.05
[0097] According to at least one embodiment of the present
invention, a side view type light emitting diode and a method of
manufacturing the same can be provided which has an overall
thickness of about 0.5 mm or lower, by sawing the mold that
surrounds the lead frames and forms the reflector using blades,
such that the thickness of the walls is about 0.04 mm to about 0.05
mm.
[0098] According to at least one embodiment of the present
invention can provide a side view type light emitting diode and a
method of manufacturing the same, in which the manufacturing
process is simplified by forming straight type electrodes without
additional processes of folding or bending, etc., when forming the
lead frames, and in which the electrical contact between the lead
frames and the conductive pattern on the PCB and the supply of
electricity are made more efficient by providing cutting-grooves on
the lead frames (at the ends of the lead frames), when mounting the
side view type light emitting diode on the PCB.
[0099] Also, one embodiment of the present invention can provide a
side view type light emitting diode with which the total quantity
of light emitted is improved, by minimizing the height of the walls
forming the reflector.
[0100] Furthermore, as the height of the walls forming the
reflector is minimized, the angle of the light emitted may be
increased, whereby the forming of dark spots can be minimized when
fitting onto the backlight device of an LCD.
[0101] While the present invention has been described with
reference to particular embodiments, it is to be appreciated that
various changes and modifications may be made by those skilled in
the art without departing from the spirit and scope of the present
invention, as defined by the appended claims and their
equivalents.
* * * * *