U.S. patent application number 13/019000 was filed with the patent office on 2011-08-11 for apparatus and method for evaluating optical properties of led and method for manufacturing led device.
Invention is credited to Il Woo Park, Jong Rak SOHN.
Application Number | 20110195531 13/019000 |
Document ID | / |
Family ID | 43927660 |
Filed Date | 2011-08-11 |
United States Patent
Application |
20110195531 |
Kind Code |
A1 |
SOHN; Jong Rak ; et
al. |
August 11, 2011 |
APPARATUS AND METHOD FOR EVALUATING OPTICAL PROPERTIES OF LED AND
METHOD FOR MANUFACTURING LED DEVICE
Abstract
An optical property evaluation apparatus includes: a light
conversion filter converting light emitted from an LED chip or a
bare LED package, which is to be evaluated, into a different
wavelength of light, and emitting a specific color of light; and an
optical property measurement unit receiving the specific color of
light emitted from the light conversion filter and measuring the
optical properties of the received light.
Inventors: |
SOHN; Jong Rak; (Hwaseong,
KR) ; Park; Il Woo; (Suwon, KR) |
Family ID: |
43927660 |
Appl. No.: |
13/019000 |
Filed: |
February 1, 2011 |
Current U.S.
Class: |
438/16 ;
257/E21.529; 356/416 |
Current CPC
Class: |
H01L 22/10 20130101;
H01L 33/50 20130101; H01L 2224/48091 20130101; G01J 1/0488
20130101; G01J 3/0251 20130101; H01L 2224/48091 20130101; H01L
2924/00014 20130101; G01J 1/04 20130101; G01J 2001/4252
20130101 |
Class at
Publication: |
438/16 ; 356/416;
257/E21.529 |
International
Class: |
H01L 21/66 20060101
H01L021/66; G01N 21/25 20060101 G01N021/25 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 5, 2010 |
KR |
10-2010-0010926 |
Feb 5, 2010 |
KR |
10-2010-0010927 |
Claims
1. An optical property evaluation apparatus comprising: a light
conversion filter converting light emitted from an LED chip or a
bare LED package, which is to be evaluated, into a different
wavelength of light, and emitting a specific color of light; and an
optical property measurement unit receiving the specific color of
light emitted from the light conversion filter and measuring the
optical properties of the received light.
2. The optical property evaluation apparatus of claim 1, wherein
the specific color of light emitted from the light conversion
filter comprises white light.
3. The optical property evaluation apparatus of claim 1, wherein
the light conversion filter comprises a phosphor filter which
converts the light emitted from the LED chip or bare LED package
into a different wavelength of light, and emits a specific color of
light.
4. The optical property evaluation apparatus of claim 3, wherein
the phosphor filter comprises a transparent substrate and a
phosphor layer formed on the transparent substrate.
5. The optical property evaluation apparatus of claim 3, wherein
the phosphor filter comprises a phosphor plate or a phosphor
film.
6. The optical property evaluation apparatus of claim 1, wherein
the light conversion filter is disposed in the vicinity of a light
reception region of the optical property measurement unit for
receiving the specific color of light.
7. The optical property evaluation apparatus of claim 1, wherein
the light conversion filter is disposed adjacent to a light
emission surface of the LED chip or bare LED package.
8. The optical property evaluation apparatus of claim 1, further
comprising a voltage application unit applying a driving voltage to
the LED chip or bare LED package which is to be evaluated.
9. The optical property evaluation apparatus of claim 1, further
comprising a light concentration unit guiding the light emitted
from the LED chip or bare LED package or the light emitted from the
light conversion filter into a light reception region of the
optical property measurement unit.
10. The optical property evaluation apparatus of claim 9, wherein
the light concentration unit comprises one of an integrating
sphere, a barrel-type light concentrator, and a bar-type light
concentrator.
11. The optical property evaluation apparatus of claim 10, wherein
the integrating sphere has an entrance opening for receiving light,
and the light conversion filter is disposed at the entrance
opening.
12. The optical property evaluation apparatus of claim 10, wherein
the integrating sphere has an exit opening for transferring light
to the light reception region of the optical property measurement
unit, and the light conversion filter is disposed at the exit
opening.
13. The optical property evaluation apparatus of claim 1, wherein
the optical property measurement unit comprises a photodiode sensor
measuring the light quality of the specific color of light emitted
from the light conversion filter and a spectrometer measuring the
spectrum of the specific color of light emitted from the light
conversion filter.
14. The optical property evaluation apparatus of claim 1, wherein
the optical property measurement unit measures the chromaticity of
the specific color of light emitted from the light conversion
filter.
15. The optical property evaluation apparatus of claim 1, wherein
the optical property measurement unit comprises a spectrometer
measuring the spectrum of the specific color of light emitted from
the light conversion filter and a calculation unit calculating a
chromaticity from the spectrum information obtained by the
spectrometer.
16. An optical property evaluation method comprising: converting
light emitted from an LED chip or bare LED package, which is to be
evaluated, into a different wavelength of light through a light
conversion filter, and emitting a specific color of light; and
receiving the specific color of light emitted from the light
conversion filter, and measuring the optical properties of the
received light.
17. The optical property evaluation method of claim 16, wherein the
specific color of light emitted from the light conversion filter
comprises white light.
18. The optical property evaluation method of claim 16, wherein the
light emitted from the LED chip or bare LED package or the light
emitted from the light conversion filter is guided into a light
reception region for receiving the specific color of light through
a light concentration unit.
19. The optical property evaluation method of claim 16, wherein the
light emitted from the LED chip or bare LED package or the light
emitted from the light conversion filter is guided into a light
reception region for receiving the specific color of light through
any one of an integrating sphere, a barrel-type light concentrator,
and a bar-type light concentrator.
20. The optical property evaluation method of claim 16, wherein the
measuring of the optical properties comprises measuring the light
quantity and spectrum of the specific color of light emitted from
the light conversion filter.
21. The optical property evaluation method of claim 16, wherein the
measuring of the optical properties comprises measuring the
chromaticity of the specific color of light emitted from the light
conversion filter.
22. A method for manufacturing an LED device, comprising: measuring
the optical properties of a specific color of light obtained by
converting light emitted from an LED chip through a light
conversion filter; and calculating a mixing ratio of
phosphor-containing resin to be applied to a resin application
process depending on the measured optical properties of the
specific color of light emitted from the light conversion filter,
based on a preset correlation between the optical properties of the
specific color of light emitted from the light conversion filter
and the optical properties of the LED device emitting the specific
color of light.
23. The method of claim 22, wherein the specific color of light
emitted from the light conversion filter comprises white light.
24. The method of claim 22, further comprising dispensing the
phosphor-containing resin prepared at the calculated mixing ratio
around the LED chip.
25. The method of claim 22, wherein the measuring of the optical
properties comprises measuring the chromaticity of the specific
color of light, and the calculating of the mixing ratio of
phosphor-containing resin comprises calculating the mixing ratio of
phosphor-containing resin to be applied to the resin application
process depending on the measured chromaticity of the specific
color of light emitted from the light conversion filter, based on
the preset correlation between the chromaticity of the specific
color of light emitted from the light conversion filter and the
chromaticity of the LED device emitting the specific color of
light.
26. A method for manufacturing an LED device, comprising: measuring
the optical properties of a specific color of light obtained by
converting light emitted from a plurality of LED chips through a
light conversion filter; classifying the plurality of LED chips
into a plurality of ranks depending on the measured optical
properties of the specific color of light emitted from the light
conversion filter; and calculating a mixing ratio of
phosphor-containing resin corresponding to the LED chips classified
into the same rank, based on a preset correlation between the
optical properties of the specific color of light emitted from the
light conversion filter and the optical properties of the LED
device emitting the specific color of light.
27. The method of claim 26, wherein the specific color of light
emitted from the light conversion filter comprises white light.
28. The method of claim 26, further comprising dispensing the
phosphor-containing resin prepared at the calculated mixing ratio
around the LED chips classified into the same rank.
29. The method of claim 26, wherein the measuring of the optical
properties comprises measuring the chromaticities of the specific
color of light, the classifying of the plurality of LED chips
comprises classifying the plurality of LED chips into a plurality
of ranks depending on the measured chromaticities of the specific
color of light, and the calculating of the mixing ratio of
phosphor-containing resin comprises calculating the mixing ratio of
phosphor-containing resin to be applied to the resin application
process depending on the ranks of the LED chips, based on the
preset correlation between the chromaticity of the specific color
of light emitted from the light conversion filter and the
chromaticity of the LED device emitting the specific color of
light.
30. An optical property evaluation method comprising: applying a
voltage to a bare LED package which is to be evaluated such that
the LED bare package emits light; and receiving the light emitted
from the bare LED package, and measuring the chromaticity of the
received light.
31. The optical property evaluation method of claim 30, wherein the
light emitted from the bare LED package is guided into a light
reception region of an optical property measurement unit through a
light concentration unit.
32. A method for manufacturing an LED device, comprising: preparing
a bare LED package; measuring the chromaticity of a specific color
of light obtained by converting light emitted from the bare LED
package through a light conversion filter; and calculating a mixing
ratio of phosphor-containing resin to be applied to a resin
application process depending on the measured chromaticity of the
specific color of light emitted from the light conversion filter,
based on a preset correlation between the chromaticity of the
specific color of light emitted from the light conversion filter
and the chromaticity of the LED device emitting the specific color
of light.
33. The method of claim 32, wherein the specific color of light
emitted from the light conversion filter comprises white light.
34. The method of claim 32, further comprising dispensing the
phosphor-containing resin prepared at the calculated mixing ratio
around an LED chip mounted on the bare LED package.
35. A method for manufacturing an LED device, comprising: preparing
a bare LED package; measuring the chromaticity of light emitted
from the bare LED package; and calculating a mixing ratio of
phosphor-containing resin to be applied to a resin application
process depending on the measured chromaticity of the light emitted
from the bare LED package, based on a preset correlation between
the chromaticity of the light emitted from the bare LED package and
the chromaticity of the LED device emitting a specific color of
light.
36. The method of claim 35, wherein the specific color of light
emitted from the LED device comprises white light.
37. The method of claim 35, further comprising dispensing the
phosphor-containing resin prepared at the calculated mixing ratio
around an LED chip mounted on the bare LED package.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priorities of Korean Patent
Application Nos. 10-2010-0010926 filed on Feb. 5, 2010 and
10-2010-0010927 filed on Feb. 5, 2010, in the Korean Intellectual
Property Office, the disclosures of which are incorporated herein
by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an apparatus and method for
evaluating the optical properties of a semiconductor light emitting
diode (LED), and more particularly, to an apparatus and method for
evaluating the optical properties of an LED and a method for
manufacturing an LED device.
[0004] 2. Description of the Related Art
[0005] A white LED device, which is currently in the spotlight as a
lighting device, is manufactured by combining a blue LED chip or an
ultraviolet (UV) LED chip with phosphors which convert the
wavelength of light emitted from the LED chip to generate visible
light. In order to obtain a target Commission Internationale de
l'Eclairage (CIE) chromaticity and a desired optical output when
manufacturing such a white LED device, the optical properties of
the LED chip and the optical properties of the phosphors should be
combined to accurately set output properties including a target CIE
chromaticity, a dominant wavelength, an optical output, and a light
speed.
[0006] To manufacture white LED devices belonging to the same white
CIE chromaticity group, the optical properties of LED chips are
measured, and the LED chips of which the optical properties are
measured to be the same rank depending on a predetermined standard
are classified into the same group. The LED chips classified into
the same group are mounted on packages, respectively, and a proper
amount (or mixing ratio) of phosphor is dispensed around the LED
chips to manufacture the white LED devices. Typically, transparent
resin including the phosphor is dispensed. For the LED chips
classified into another group, a different amount (or mixing ratio)
of phosphor may be dispensed. Then, the optical properties of the
manufactured white LED devices are measured, and the white LED
devices which satisfy target optical efficiency and a target white
CIE chromaticity are classified and shipped.
[0007] In the above-described processes, the process of measuring
the optical properties of the LED chips is referred to as a probing
process. Depending on how the optical properties of the LED chips
are measured by the probing process and how the LED chips are
classified depending on the measurement result, the production
yield of the white LED devices may be decided. In general, the
optical properties of LED chips having an effect upon the optical
properties of white LED devices include a wavelength and an optical
output. When the LED chips are classified depending on the optical
properties, a dominant wavelength or peak wavelength may be used as
the wavelength, and the optical output may be used in unit of mV or
mcd. When the LED chips are classified depending on the wavelength
and the optical output, the LED chips may be classified in such a
manner as to have the correlation with the optical properties of
white LED devices which are to be manufactured. However, it is
difficult to accurately measure variations in wavelength or optical
output depending on viewing angles. Furthermore, when the optical
properties of the LED chips are measured, a short wavelength of
light such as blue light or UV light is measured. Therefore, the
variation of the optical properties is very small. Accordingly, it
is very difficult to measure the optical properties of the LED
chips such that the optical properties have the correlation with
the optical properties of the white LED devices. Hence, although
LED chips classified into the same group are used to manufacture
white LED devices through the same package process, the white LED
devices may exhibit different chromaticities and optical outputs,
and some of them may exhibit chromaticities deviating from the
target chromaticity range.
[0008] An apparatus for measuring the optical properties of an LED
according to the related art receives monochromatic light such as
blue light or UV light emitted from LED chip and measures the light
quantities and wavelengths of the monochromatic light. Depending on
the measured light quantities and wavelengths, LED chips having a
constant optical property are grouped and classified. However,
despite the variations in wavelength, the movement of the
chromaticities of blue or UV LED chips used in the white LED
devices is much smaller than that of the chromaticities of the
white LED devices. Accordingly, although the blue or UV LED chips
are classified into the same group depending on the light
quantities and wavelengths, the chromaticities of the white LED
devices implemented by dispensing phosphor to the LED chips have
considerably wide distribution. Light quantity (luminous intensity
or optical output) has a close relationship with chromaticity. For
example, when a white LED device is implemented by using a blue LED
chip and yellow phosphor, the chromaticity of the white LED device
differs depending on the ratio of the quantity of blue light to the
quantity of yellow light which is obtained from the phosphor by the
blue light. Therefore, when a slight difference occurs in the light
quantity of the blue light, the chromaticity of the white LED
device is varied, and the white light is affected.
[0009] Furthermore, due to a deviation between elements of the
white LED devices, including an LED chip, a package body, a lead
frame, a phosphor, and a sealing agent, a target chromaticity may
be not obtained. Therefore, it is difficult to finely control the
chromaticity of the white LED device to the target chromaticity by
classifying the LED chips through the chip probing. The
chromaticity of the white LED device may be affected by the shape
of a lead frame, the position of the LED chip inside the package,
and the amount of resin sealing agent to be dispensed. However,
main factors of the chromaticity distribution of the white LED
device may not be discriminated. Accordingly, the cause of the
chromaticity distribution may not be properly investigated, and
there is a considerable obstacle to improving the production yield
of the white LED devices in terms of the chromaticity.
[0010] To reduce the chromaticity distribution of white
chromaticities, a small number of LED chips may be sampled before
phosphor-containing resin is dispensed, that is, before the
dispensing process. Then, the dispensing process may be performed
on the sampled LED chips to finely control the chromaticity
thereof. In this case, since the entire process (curing and so on)
after the dispensing process is performed until the chromaticities
of the sampled chips reach the target chromaticity, there is a
considerable amount of cost and time consumption involved.
Furthermore, the target chromaticity is not always guaranteed for
the LED chips other than the sampled LED chips.
[0011] The combination of monochromatic light emitted from the LED
chip and light emitted from the phosphor may generate a specific
color of light other than white light. Even when an LED device
outputting a specific color of light other than white light is
manufactured, it is necessary to realize the target chromaticity,
to reduce the chromaticity distribution, and to increase the
yield.
SUMMARY OF THE INVENTION
[0012] According to an aspect of the present invention, there is
provided an optical property evaluation apparatus including: a
light conversion filter converting light emitted from an LED chip
or a bare LED package, which is to be evaluated, into a different
wavelength of light, and emitting a specific color of light; and an
optical property measurement unit receiving the specific color of
light emitted from the light conversion filter and measuring the
optical properties of the received light. The specific color of
light emitted from the light conversion filter may include white
light.
[0013] According to another aspect of the present invention, there
is provided an optical property evaluation method including:
converting light emitted from an LED chip or a bare LED package,
which is to be evaluated, into a different wavelength of light
through a light conversion filter, and emitting a specific color of
light; and receiving the specific color of light emitted from the
light conversion filter, and measuring the optical properties of
the received light.
[0014] According to another aspect of the present invention, there
is provided a method for manufacturing an LED device, including:
measuring the optical properties of a specific color of light
obtained by converting light emitted from an LED chip through a
light conversion filter; and calculating a mixing ratio of
phosphor-containing resin to be applied to a resin application
process depending on the measured optical properties of the
specific color of light emitted from the light conversion filter,
based on a preset correlation between the optical properties of the
specific color of light emitted from the light conversion filter
and the optical properties of the LED device emitting the specific
color of light. The specific color of light emitted from the light
conversion filter may include white light.
[0015] According to another aspect of the present invention, there
is provided a method for manufacturing an LED device, including:
measuring the optical properties of a specific color of light
obtained by converting light emitted from a plurality of LED chips
through a light conversion filter; classifying the plurality of LED
chips into a plurality of ranks depending on the measured optical
properties of the specific color of light emitted from the light
conversion filter; and calculating a mixing ratio of
phosphor-containing resin corresponding to the LED chips classified
into the same rank, based on a preset correlation between the
optical properties of the specific color of light emitted from the
light conversion filter and the optical properties of the LED
device emitting the specific color of light.
[0016] According to another aspect of the present invention, there
is provided an optical property evaluation method including:
applying a voltage to a bare LED bare package which is to be
evaluated such that the bare LED package emits light; and receiving
the light emitted from the bare LED package, and measuring the
chromaticity of the received light.
[0017] According to another aspect of the present invention, there
is provided a method for manufacturing an LED device, including:
preparing a bare LED package; measuring the chromaticity of a
specific color of light obtained by converting light emitted from
the bare LED package through a light conversion filter; and
calculating a mixing ratio of phosphor-containing resin to be
applied to a resin application process depending on the measured
chromaticity of the specific color of light emitted from the light
conversion filter, based on a preset correlation between the
chromaticity of the specific color of light emitted from the light
conversion filter and the chromaticity of the LED device emitting
the specific color of light.
[0018] According to another aspect of the present invention, there
is provided a method for manufacturing an LED device, including:
preparing a bare LED package; measuring the chromaticity of light
emitted from the bare LED package; and calculating a mixing ratio
of phosphor-containing resin to be applied to a resin application
process depending on the measured chromaticity of the light emitted
from the bare LED package, based on a preset correlation between
the chromaticity of the light emitted from the bare LED package and
the chromaticity of the LED device emitting a specific color of
light.
[0019] In this specification, the bare LED package refers to a
package structure in which an LED chip is mounted on a package body
and phosphor-containing resin is not yet dispensed. For example, a
package structure in which an LED chip is die-bonded to a package
body before phosphor-containing resin is dispensed or die-bonding
and wire-bonding are completed corresponds to the bare LED
package.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The above and other aspects, features and other advantages
of the present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0021] FIG. 1 is a schematic view of an apparatus for evaluating
the optical properties of an LED chip according to an embodiment of
the present invention;
[0022] FIGS. 2A and 2B are diagrams illustrating examples of a
light conversion filter which may be used in the embodiment of the
present invention;
[0023] FIG. 3 is a schematic view of an apparatus for evaluating
the optical properties of an LED chip according to another
embodiment of the present invention;
[0024] FIG. 4 is a schematic view of an apparatus for evaluating
the optical properties of an LED chip according to another
embodiment of the present invention;
[0025] FIG. 5 is a diagram illustrating an apparatus for evaluating
the optical properties of an LED chip according to another
embodiment of the present invention;
[0026] FIG. 6 is a diagram showing a process of evaluating the
optical properties of a white LED device including an LED chip and
phosphor;
[0027] FIGS. 7A and 7B show the spectrum and chromaticity of white
light obtained from a light conversion filter according to the
embodiment of the present invention;
[0028] FIGS. 8A and 8B show the spectrum and chromaticity of white
light emitted from a white LED device;
[0029] FIG. 9 is a flow chart explaining a method for evaluating
the optical properties of an LED chip according to another
embodiment of the present invention;
[0030] FIG. 10 is a flow chart explaining a method for
manufacturing a white LED device according to another embodiment of
the present invention;
[0031] FIG. 11 is a flow chart showing a method for manufacturing a
white LED device according to another embodiment of the present
invention;
[0032] FIG. 12 is a schematic view of an apparatus for evaluating
the optical properties of an LED chip according to another
embodiment of the present invention;
[0033] FIGS. 13A and 13B are diagrams illustrating examples of a
light conversion filter which may be used in this embodiment of the
present invention;
[0034] FIG. 14 is a schematic view of an apparatus for evaluating
the optical properties of an LED chip according to another
embodiment of the present invention;
[0035] FIG. 15 is a schematic view of an apparatus for evaluating
the optical properties of an LED chip according to another
embodiment of the present invention;
[0036] FIG. 16 is a diagram illustrating an apparatus for
evaluating the optical properties of an LED chip according to
another embodiment of the present invention;
[0037] FIG. 17 is a diagram showing a process of evaluating the
optical properties of a white LED device including an LED chip and
phosphor;
[0038] FIGS. 18A and 18B show the spectrum and chromaticity of
white light obtained from a light conversion filter according to
the embodiment of the present invention;
[0039] FIGS. 19A and 19B show the spectrum and chromaticity of
white light emitted from a white LED device;
[0040] FIG. 20 is a flow chart explaining a method for evaluating
the optical properties of an LED chip according to another
embodiment of the present invention;
[0041] FIG. 21 is a flow chart explaining a method for evaluating
the optical properties of an LED according to another embodiment of
the present invention;
[0042] FIG. 22 is a flow chart explaining a method for
manufacturing a white LED device according to another embodiment of
the present invention; and
[0043] FIG. 23 is a flow chart explaining a method for
manufacturing a white LED device according to another embodiment of
the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0044] Exemplary embodiments of the present invention will now be
described in detail with reference to the accompanying drawings.
The invention may, however, be embodied in many different forms and
should not be construed as being limited to the embodiments set
forth herein. Rather, these embodiments are provided so that this
disclosure will be thorough and complete, and will fully convey the
scope of the invention to those skilled in the art. In the
drawings, the thicknesses of layers and regions are exaggerated for
clarity. Like reference numerals in the drawings denote like
elements, and thus their description will be omitted.
[0045] FIG. 1 is a diagram schematically illustrating an apparatus
for evaluating the optical properties of an LED chip according to
an embodiment of the present invention. According to the embodiment
of the present invention, white light is emitted through light
conversion filters 151 and 152 in a probing operation of the LED
chip, and the optical properties of the emitted white light, such
as chromaticity, are measured. The chromaticity of the white light
obtained through the light conversion filters 151 and 152 may have
a clear correlation with the chromaticity of a white LED device
which has been manufactured by dispensing a phosphor. The
correlation may be used to calculate a proper mixing ratio of
phosphor-containing resin from the chromaticity of the white light
(obtained through the light conversion filters) which is obtained
in the probing operation of the LED chip 50.
[0046] Referring to FIG. 1, the optical property evaluation
apparatus 100 includes the light conversion filters 151 and 152
which convert light emitted from an LED chip 50 which is to be
evaluated, or monochromatic light, for example, blue light or UV
light, into a different wavelength of light, and emit white light.
The white light emitted through the light conversion filters 151
and 152 is received by optical property measurement units to
measure the optical properties of the white light. The optical
property measurement units may include a photodiode sensor 130
measuring a light quantity (optical power) and a spectrometer 140
measuring a spectrum.
[0047] Referring to FIG. 1, the LED chip 50 receives a voltage
through probe pins 105 of a probe card 115 and emits monochromatic
light, for example, blue light or UV light. The probe card 115
corresponds to a voltage application unit applying a driving
voltage to the LED chip 50 or a portion of the voltage application
unit. The monochromatic light emitted from the LED chip 50 is
reflected by an integrating sphere 110 and concentrated on light
reception regions. The integrating sphere 110 has exits for
transferring the light to the light reception regions of the
optical property measurement units including the photodiode sensor
130 and the spectrometer 140. The light conversion filters 151 and
152 installed in the light reception regions (in particular, the
exit openings of the integrating sphere 110) adjacent to the
optical property measurement units including the photodiode sensor
130 and the spectrometer 140 converts the light emitted from the
LED chip 50 into a different wavelength of light to obtain white
light.
[0048] The white light obtained through the light conversion filter
151 or 152 is transmitted through an optical cable 102 or 121 to
the photodiode sensor 130 or the spectrometer 140 to measure an
optical property of the white light such as light quantity or
spectrum. The optical property measurement units measure the
chromaticity of the white light obtained through the light
conversion filters 151 and 152 from the spectrum of the white light
obtained by the spectrometer 140. According to the embodiment of
the present invention, the light conversion filters are used to
measure the chromaticity of the white light converted from the
monochromatic light in the optical property measurement operation
for the LED chip. Therefore, it is possible to obtain the
chromaticity of the white light which is decided by the optical
properties of the LED chip in the chip probing operation before a
die boning or chip bonding operation or a phosphor dispensing
operation.
[0049] The chromaticity of the white light obtained through the
light conversion filters 151 and 152 has a clear correlation with
the chromaticity of a white LED device which has been manufactured
by dispensing a phosphor. Based on the correlation between the
optical properties (chromaticity and so on) of the white light
obtained through the light conversion filters and the optical
properties (chromaticity and so on) of the white LED device
manufactured by dispensing a phosphor to an LED chip, a mixing
ratio of phosphor-containing resin for obtaining a target
chromaticity of the white LED device may be calculated from the
chromaticity of the white light (obtained through the light
conversion filters) which is measured by the above-described
optical property evaluation apparatus 100. The mixing ratio may
include a ratio of phosphor to transparent resin and a ratio of two
or more different phosphors. Furthermore, the correlation may be
used to infer the luminance intensity of the white LED device from
the optical properties of the white light obtained through the
light conversion filters 151 and 152. Since the mixing ratio of the
phosphor-containing resin for realizing the target white
chromaticity may be more precisely calculated in the chip probing
operation (optical property evaluation operation) by using the
correlation between the optical properties, it is possible to
significantly improve the production yield and productivity of the
white LED device.
[0050] Depending on the optical properties of the white light
obtained through the light conversion filters 151 and 152, LED
chips may be classified into a plurality of ranks. This is
different from an existing method which classifies the ranks of LED
chips depending on the optical properties of light (monochromatic
light) emitted from the LED chips. In this embodiment of the
present invention, the LED chips may be more precisely classified
by using the correlation with the optical properties (chromaticity
and so on) of the white LED device. Such classification makes it
possible to accurately decide the mixing ratio of
phosphor-containing resin for realizing the target chromaticity of
the white LED device.
[0051] The correlation between the optical properties, which is
used for calculating the mixing ratio of phosphor-containing resin
for obtaining the target chromaticity of the white LED device or
the luminous intensity of the white LED device, may be calculated
based on the optical properties of the white light measured by the
optical property evaluation apparatus 100 and the optical
properties of the white LED device which has been manufactured. For
example, the above-described optical property evaluation apparatus
100 may be used to measure the optical properties of white light
(obtained through the light conversion filter) for a sufficient
number of LED chip samples, and the optical properties of white
light emitted from white LED devices which are manufactured by
using the LED chip samples and various mixing ratios of
phosphor-containing resin may be measured. Then, the optical
properties of the two kinds of white light may be compared in order
to set the correlation between the optical properties. Based on the
correlation between the optical properties of the white light
emitted from the light conversion filters and the optical
properties of the white light emitted from the white LED device,
the mixing ratio of phosphor to transparent resin for obtaining the
target chromaticity, the mixing ratio of two or more different
phosphors, and the luminous intensity of the white LED device may
be calculated or predicted in the chip probing operation.
[0052] The light conversion filters 151 and 152 used for converting
light emitted from the LED chip into white light during the optical
property measurement may be formed of an arbitrary material which
is capable of converting a short wavelength of light into a long
wavelength of light to obtain white light. In particular, a
phosphor which converts monochromatic light emitted from the LED
chip, such as blue light or UV light, into a different wavelength
of light to obtain white light maybe used in the light conversion
filters 151 and 152.
[0053] FIGS. 2A and 2B are diagrams illustrating examples of the
light conversion filter which may be used in the embodiment of the
present invention. FIG. 2A illustrates a light conversion filter
150 in which a phosphor layer 150b is uniformly applied onto a
transparent substrate 150a such as glass, quartz, or plastic, and
FIG. 2A illustrates a phosphor plate or phosphor film 150' which
may be used as the above-described light conversion filter. The
phosphor layer 150b and the phosphor plate or phosphor film 150'
maybe formed of phosphor-containing resin. The phosphor plate or
phosphor film 150' maybe prepared by the following process. For
example, phosphor powder particles may be dispersed in a
transparent resin solvent and then cured into a plate or film
form.
[0054] The light conversion filters 150 and 150' may be used as the
light conversion filters 151 and 152 of the optical property
evaluation apparatus 100 according to the embodiment of the present
invention. For example, when the LED chip 50 to be evaluated is a
blue LED chip, the phosphor used in the light conversion filters
150 and 150' may be a yellow phosphor which converts blue light
into yellow light. Furthermore, when the LED chip 50 is a blue LED
chip, a mixture of a red phosphor and a green phosphor maybe used
in the light conversion filters 150 and 150'. When the LED chip 50
is a UV LED chip, a mixture of a red phosphor, a green phosphor,
and a blue phosphor may be used in the light conversion filters 150
and 150'. The phosphors used in the light conversion filters may
include various phosphors such as a garnet-based phosphor, a
silicate-based phosphor, a nitride-based phosphor, a sulfide-based
phosphor, a halogen compound-based phosphor, an aluminate-based
phosphor, and an oxide-based phosphor. In addition, various shapes,
combinations, and compositions of phosphors capable of realizing
white light may be used in the light conversion filters.
[0055] FIG. 3 is a schematic view of an apparatus for evaluating
the optical properties of an LED chip according to another
embodiment of the present invention. The optical property
evaluation apparatus 100' according to the embodiment of the
present invention includes a light conversion filter 153 disposed
adjacent to a light emission surface of the LED chip 50. The light
conversion filter 153 converts the wavelength of light emitted from
the LED chip 50. Referring to FIG. 3, when an integrating sphere 10
is used to concentrate light, the light conversion filter 153 may
be disposed at an entrance opening of the integrating sphere 110,
through which the light emitted from the LED chip 50 is received
into the integrating sphere 110. Therefore, white light emitted
through the light conversion filter 153 is concentrated by the
integrating sphere 110 and enters light reception regions of
optical property measurement units including a photodiode sensor
130 and a spectrometer 140 to measure the optical properties of the
white light. The other components, functions, and effects are same
as those of the above-described embodiment.
[0056] FIG. 4 is a diagram illustrating an apparatus 200 for
evaluating the optical properties of an LED chip according to
another embodiment of the present invention. In the above-described
embodiments of the present invention, the integrating sphere 110 is
used as a light concentration unit for guiding the light emitted
from the LED chip 50 or the light conversion filter to the light
reception regions of the optical property measurement units (refer
to FIGS. 1 and 3). In this embodiment of the present invention,
however, a barrel-type light concentrator 111 is used instead of
the integrating sphere. The light emitted from the LED chip 50, for
example, blue light or UV light, is converted by a light conversion
filter 154 disposed in the barrel-shaped concentrator 111. Then,
white light is emitted from the light conversion filter 154, and
enters a light reception region of optical property measurement
units including a photodiode sensor 130 and a spectrometer 140. The
luminous intensity, spectrum, wavelength, and chromaticity of the
white light may be measured by the optical property measurement
units.
[0057] The light conversion filter 154 may be disposed at various
positions. For example, the light conversion filter 154 maybe
disposed at a central portion B inside the barrel-type light
concentrator 111 or an entrance portion A of the barrel-type light
concentrator 111. Furthermore, the light conversion filter 154 may
be disposed at an exit portion C of the barrel-type light
concentrator 111 or the light reception region D of the optical
property measurement units. The other components and the functions
thereof are the same as those of the above-described
embodiments.
[0058] FIG. 5 is a diagram illustrating an apparatus 300 for
evaluating the optical properties of an LED chip according to
another embodiment of the present invention. Referring to FIG. 5,
the optical property evaluation apparatus 300 according to the
embodiment of the present invention includes a bar-type light
concentrator 112 which is used as a light concentration unit for
guiding light emitted from the LED chip 50 or a light conversion
filter into a light reception region of optical property
measurement units, instead of the integrating sphere or the
barrel-type light concentrator. The bar-type light concentrator 112
has a narrow internal space. The light emitted from the LED chip 50
is converted by the light conversion filter 155. Then, white light
is emitted from the light conversion filter 155, and the optical
properties of the white light such as a chromaticity are measured
by the optical property measurement units including a photodiode
sensor 130 and a spectrometer 140. The light conversion filter 155
may be disposed at various positions A', B', and C' inside the
bar-type light concentrator 112.
[0059] The variety of optical property evaluation apparatuses 100,
100', 200, and 300 according to the embodiments of the present
invention may be used to measure the optical properties of light
emitted from an LED chip in a white chromaticity region. The
measured optical properties of the white light may be compared with
the optical properties of a white LED device which has been
manufactured by applying phosphor-containing resin to the LED chip.
Through the comparison, it is possible to establish or set the
correlation between the optical properties of the white light
obtained in the chip probing operation and the optical properties
of the white LED device. The established correlation may be used
for calculating a mixing ratio of phosphor-containing resin which
is to be applied to the LED chip to manufacture a white LED device
within the target chromaticity range.
[0060] FIG. 6 is a diagram showing a process of evaluating the
optical properties of a white LED device 70 which has been
manufactured by dispensing phosphor-containing resin to the LED
chip 50. The white LED device 70 may be manufactured by the
following process. First, the LED chip 50, for example, a blue LED
chip is mounted on a package body 55, and wire bonding for
electrical connection is performed. Then, phosphor-containing
resin, for example, yellow phosphor-containing resin is dispensed
around the LED chip 50 and cured. Before the white LED device 70 is
manufactured, the optical properties of the LED chip 50 such as
chromaticity are measured by the above-described optical property
evaluation apparatus 100, 100', 200', or 300. The optical
properties of white light emitted from the manufactured white LED
device 70 may be measured by a typical optical property measurement
apparatus for a white LED device. The white light emitted from the
white LED device is transferred to a measurement unit (not shown)
through a light reception unit 210 and an optical cable 220 of the
optical property measurement apparatus. The optical properties of
the white light, such as luminous intensity and chromaticity, may
be measured by the measurement unit.
[0061] Referring to FIG. 6, the optical properties of the white
light emitted from the white LED device which has been manufactured
may be compared with the optical properties of the white light
(emitted from the light conversion filter) which are measured by
the optical property evaluation apparatus 100, 100', 200, or 300
before the white LED device is manufactured. Then, it is possible
to establish the correlation data between the optical
properties.
[0062] FIGS. 7A and 7B show the spectrum and chromaticity of the
white light obtained from the light conversion filter 151, 152,
153, 154, or 155 in the chip probing operation. FIGS. 8A and 8B
show the spectrum and chromaticity of the white light emitted from
the white LED device manufactured by applying phosphor-containing
resin to the LED chip having the properties of FIG. 7. The
phosphor-containing resin within the white LED device is prepared
at a well-known mixing ratio. A sufficient number of LED chip
samples and well-known mixing ratios may be used to compare and
analyze the chromaticity of FIG. 7B and the chromaticity of FIG.
8B. Then, it is possible to establish and set the correlation
between the chromaticity of the white light obtained from the light
conversion filter in the chip probing operation and the
chromaticity of the white light obtained from the white LED device,
with respect to various mixing ratios. In FIGS. 7B and 8B, ranks
depending on chromaticities may be classified into several regions.
Based on the rank classification, it is possible to establish the
correlation between the chromaticity rank of the white light
emitted from the light conversion filter and the chromaticity rank
of the white light emitted from the white LED device.
[0063] FIG. 9 is a flow chart explaining a method for evaluating
the optical properties of an LED chip according to another
embodiment of the present invention. The optical property
evaluation method may be performed by using the optical property
evaluation apparatuses 100, 100', 200', and 300 according to the
above-described embodiments of the present invention.
[0064] Referring to FIG. 9, light emitted from an LED chip which is
to be evaluated is converted by the light conversion filter 151,
152, 153, 154, or 155, and white light is emitted from the light
conversion filter (S11). The white light emitted from the light
conversion filter enters the light reception region of the optical
property measurement unit including a photodiode sensor and a
spectrometer, and the optical properties of the white light such as
wavelength, luminous intensity, and chromaticity are measured
(S12).
[0065] The monochromatic light emitted from the LED chip may be
guided into the light reception region of the optical property
measurement unit through the light concentration unit such as the
integrating sphere, the barrel-type light concentrator, or the
bar-type light concentrator, before the monochromatic light is
converted by the light conversion filter (refer to FIG. 1).
Alternatively, the monochromatic light emitted from the LED chip
may be converted by the light conversion filter, and the white
light emitted from the light conversion filter may be guided into
the light reception region of the optical property measurement unit
through the light concentration unit such as the integrating
sphere, the barrel-type light concentrator, or the bar-type light
concentrator (refer to FIG. 3).
[0066] In the optical property measurement operation S12, the light
quantity of the white light emitted from the light conversion
filter may be measured through the photodiode sensor, and the
spectrum of the white light may be measured through the
spectrometer. Furthermore, the chromaticity of the white light
emitted from the light conversion filter maybe measured in the
optical property measurement operation S12.
[0067] The above-described optical property evaluation method may
be utilized to manufacture a white LED device at a high production
yield and productivity. In particular, the above-described optical
property evaluation apparatus or method may be used for
manufacturing a white LED device satisfying a target chromaticity
at a high yield.
[0068] FIG. 10 is a flow chart explaining a method for
manufacturing a white LED device according to another embodiment of
the present invention. Referring to FIG. 10, an LED chip is
prepared (S101). The LED chip may be a blue LED chip or a UV LED
chip. Next, the optical properties of the LED chip are measured in
accordance with the above-described optical property evaluation
method (refer to FIG. 9) (S102). In the optical property
measurement operation S102, light emitted from the LED chip is
converted by a light conversion filter. Then, white light is
emitted from the light conversion filter, and the optical
properties of the white light such as chromaticity and so on are
measured.
[0069] Subsequently, based on the above-described correlation
between the optical properties, that is, the preset correlation
between the optical properties of the white light emitted from the
light conversion filter and the optical properties of the white
light emitted from the white LED device, a mixing ratio of
phosphor-containing resin which is to be applied to manufacture the
white LED device is calculated from the optical properties measured
in operation S102 (S103). In this case, the correlation between the
chromaticities, among the correlations between the optical
properties, may be used to calculate the mixing ratio of the
phosphor-containing resin. That is, based on the preset correlation
between the chromaticity of the white light emitted from the light
conversion filter and the chromaticity of the white LED device, the
mixing ratio of the phosphor-containing resin may be calculated in
accordance with the chromaticity of the white light (emitted from
the light conversion filter) which is measured in operation
S102.
[0070] Then, the phosphor-containing resin prepared at the
calculated mixing ratio may be dispensed around the LED chip to
manufacture the white LED device (S104). Before the
phosphor-containing resin is dispensed, a chip bonding operation
and a wire bonding operation may be performed, as in a process for
manufacturing a typical white LED device.
[0071] The above-described method for manufacturing the white LED
device may additionally include classifying the ranks of the LED
chips to manufacture a plurality of white LED devices. FIG. 11 is a
flow chart showing a method for manufacturing a white LED device
according to another embodiment of the present invention, in which
a process for classifying the ranks of LED chips is considered. The
ranks of the LED chips may be classified depending on the optical
properties of white light emitted from the light conversion filter,
rather than the optical properties of monochromatic light emitted
from the LED chips.
[0072] Referring to FIG. 11, a plurality of LED chips are prepared
(S201). Then, the optical properties of white light obtained by the
LED chips and the light conversion filter are measured by the
above-described optical property evaluation method (S202).
Depending on the measured optical properties of the white light,
the plurality of LED chips are classified into a plurality of ranks
(S203). For example, the ranks of the LED chips may be classified
depending on the chromaticities of the white light emitted from the
light conversion filter.
[0073] Based on the above-described preset correlation between the
optical properties, a mixing ratio of phosphor-containing resin
corresponding to the LED chips classified in the same rank is
calculated (S204). For example, based on the preset correlation
between the chromaticity of the white light emitted from the light
conversion filter and the chromaticity of the white light emitted
from the white LED device, the mixing ratio of phosphor-containing
resin may be calculated depending on the ranks of the LED chips.
The phosphor-containing resin prepared at the mixing ratio
calculated depending on the ranks is dispensed around the LED
chips. That is, the phosphor-containing resin prepared at the
calculated mixing ratio is dispensed to the LED chips classified
into the same rank to manufacture the white LED devices (S205).
[0074] When the above-described manufacturing method is used, the
optical property ranks of the LED chips may be more precisely
classified, and the mixing ratio of the phosphor-containing resin
required for realizing the target chromaticity may be more
accurately calculated. Accordingly, the production yield of the
white LED devices within the target chromaticity increases, and
productivity thereof is improved.
[0075] In the above-described embodiments, it has been described
that white light is emitted from the light conversion filters 150,
150', 151, 152, 153, 154, and 155. Furthermore, the method for
manufacturing the white LED device which emits white light by
mixing monochromatic light emitted from the LED chip and light
emitted from phosphor has been described. However, the embodiments
of the present invention are not limited to such cases. That is,
the embodiments of the present invention may be also applied to a
case in which a specific color of light other than white light is
emitted from the light conversion filters 150, 150', 151, 152, 153,
154, and 155. For example, the light conversion filter maybe used
to convert red light emitted from a red LED chip into a different
wavelength of light, and the converted light and the red light
maybe mixed to finally emit purple light as the mixed light. The
chromaticity and/or light quantity of the specific color of light
emitted from the light conversion filter maybe measured to evaluate
the optical properties of LED chips used in specific color LED
devices other than the white LED device. Accordingly, the ranks of
the LED chips may be classified, which makes it possible to reduce
the chromaticity distribution of the specific color LED
devices.
[0076] According to the above-described embodiments, when the
optical properties of an LED chip are measured, the light
conversion filter is used to measure a specific color of light such
as white light. Therefore, the correlation between the optical
properties of the LED chip and the optical properties of a specific
color LED device including the LED chip becomes clear. The
correlation may be used to more accurately calculate the mixing
ratio of phosphor-containing resin for realizing the target
chromaticity. Accordingly, the chromaticity distribution of LED
devices emitting a specific color of light such as white light may
decrease, and the production yield and productivity of the LED
devices may increase. Furthermore, in the optical property
evaluation operation, a specific color of light, such as white
light, is implemented to classify the LED chips. Therefore, when
specific color LED devices are manufactured, the chromaticity and
brightness of the specific color LED devices may be more accurately
predicted to classify the LED chips.
[0077] FIG. 12 is a schematic view of an apparatus for evaluating
the optical properties of an LED chip according to another
embodiment of the present invention. The optical property
evaluation apparatus 100 emits white light through a light
conversion filter 151 during a process of evaluating light emitted
from a bare LED package 50, and measures the chromaticity of the
emitted white light. The bare LED package 50 refers to a package in
which an LED chip 10 is die-bonded to a package body 20 and, if
necessary, connected to a lead frame (not shown) of the package
body 20 through wire bonding. The bare LED package 50 corresponds
to an intermediate product before phosphor-containing resin, for
example, a sealing agent having phosphors dispersed therein is
dispensed. The package body 20 may include a reflecting cup in
which the LED chip 10 is mounted. The chromaticity of white light
obtained through a light conversion filter 151 may have a clear
correlation with the chromaticity of a white LED device which has
been manufactured by dispensing phosphor-containing resin. Based on
the correlation, a proper mixing ratio of phosphor-containing resin
for realizing a target chromaticity of the white LED device may be
calculated from the chromaticity of the white light obtained
through the light conversion filter 151.
[0078] The optical property evaluation apparatus 100 according to
the embodiment of the present invention evaluates the optical
properties of the bare package having the LED chip 50 mounted on
the package body 20 through the light conversion filter, different
from an existing LED chip probing apparatus which evaluates the
optical properties of an LED chip. Since the evaluation result of
the optical properties of the bare package is used to calculate a
proper mixing ratio of phosphor-containing resin to be dispensed
when the white LED device is manufactured, it is possible to reduce
white chromaticity distribution which is caused by such factors as
the position of the LED chip inside the package and the shape of
the lead frame.
[0079] Referring to FIG. 12, the optical property evaluation
apparatus 100 according to the embodiment of the present invention
includes a light conversion filter 151 which converts light emitted
from the bare LED package 50, for example, blue light or UV light
into a different wavelength of light and emits white light. The
white light emitted through the light conversion filter 151 is
received by an optical property measurement unit 140 to measure the
optical properties of the white light such as chromaticity. The
optical property measurement unit 140 may include a spectrometer
141 and a calculation unit 142. The spectrometer 141 measures the
spectrum of the white light emitted from the light conversion
filter 151, and the calculation unit 142 such as a computer
calculates a chromaticity from the spectrum information obtained
from the spectrometer 141.
[0080] Referring to FIG. 12, the bare LED package 50 receives a
driving voltage from a voltage application unit 100 such as a
driving board, and emits blue light or UV light, for example. The
light emitted from the bare LED package 50 enters a barrel-type
light concentrator 110. At least some of the light entering the
light concentrator 110 may be reflected by the inner wall of the
light concentrator 110, and converted into a different wavelength
of light by the light conversion filter 151 disposed inside the
light concentrator 110. Then, white light is emitted from the light
conversion filter 151 to enter the optical property measurement
unit 140 through a light reception region. The optical property
measurement unit 140 measures the chromaticity of the white light.
According to the embodiment of the present invention, the light
conversion filter 151 is used in the optical property evaluation
operation for the bare LED package to measure the chromaticity of
the white light converted from monochromatic light or non-white
light. Therefore, it is possible to obtain the chromaticity of the
white light, which is decided by the optical properties of the bare
LED package 50, in a state of the bare package before the phosphor
dispensing.
[0081] The white light obtained through the light conversion filter
151 has a clear correlation with the chromaticity of a white LED
device which has been manufactured by dispensing phosphors. Based
on the correlation between the chromaticity of the white light
obtained from the bare LED package 50 through the light conversion
filter 151 and the chromaticity of a white LED device 70 (refer to
FIG. 17) manufactured by dispensing phosphors to the bare LED
package 50, a mixing ratio of phosphor-containing resin for
obtaining a target chromaticity of the white LED device maybe
calculated from the chromaticity of the white light (obtained
through the light conversion filter) which is measured by the
above-described optical property evaluation apparatus 100. The
mixing ratio may include a ratio of phosphor to transparent resin
and a ratio of two or more different phosphors. When the
above-described correlation between the chromaticities is used, it
is possible to more accurately calculate the mixing ratio of
phosphor-containing resin in the state of the bare LED package 50.
Therefore, it is possible to significantly improve the production
yield and productivity of the white LED device. Furthermore, since
the bare LED package 50 which is to be evaluated already has the
LED chip 10 mounted on the package body 2, the mounting position of
the LED chip 10 and the shape of the lead frame do not need to be
considered as factors having an effect upon the chromaticity of the
white LED device. In an LED chip evaluation operation using an
existing chip prober, although it is evaluated that LED chips have
the same optical property, a considerable deviation may occur in
the chromaticities of final white LED devices due to such factors
as the shape of lead frames and the mounting position of the LED
chips.
[0082] Depending on the mixing ratio of phosphor-containing resin
dispensed around the LED chip, for example, the ratio of a phosphor
to transparent resin or the ratio of two or more different kinds of
phosphors, the chromaticity of the white LED device may differ or
may be decided. Therefore, the mixing ratio of phosphor-containing
resin may serve as an important factor for realizing the target
white chromaticity. As described above, the correlation used for
calculating the mixing ratio of phosphor-containing resin for
obtaining the target white chromaticity of the white LED device may
be calculated based on the chromaticity of the white light measured
by the above-described optical property evaluation apparatus and
the chromaticity measured in the white LED device 100.
[0083] For example, the above-described optical property evaluation
apparatus 100 may be used to measure the chromaticities of white
light obtained from a sufficient number of bare LED package samples
through the light conversion filter, and the chromaticities of
white light emitted from white LED devices manufactured by using
the bare LED package samples and various mixing ratios of
phosphor-containing resin. Then, the chromaticities of two kinds of
white light may be compared to set the correlation between the
chromaticities. The correlation set in such a manner, that is, the
correlation between the chromaticity of the white light emitted
from the light conversion filter and the chromaticity of the white
light emitted from the white LED device may be used to calculate or
predict the mixing ratio of phosphor to transparent resin for
obtaining the target white chromaticity and the mixing ratio of two
or more different phosphors in the bare LED package evaluation
operation.
[0084] As the light conversion filter 151 used for converting the
light emitted from the bare LED package 50 into white light, an
arbitrary material capable of converting a short wavelength of
light into a long wavelength of light to emit white light may be
used. In particular, a phosphor material which converts
monochromatic light emitted from the bare LED package 50, such as
blue light or UV light, into a different wavelength of light to
emit white light may be used in the light conversion filter
151.
[0085] The light conversion filter 151 may be disposed at any
position inside the barrel-type light concentrator 110. FIG. 12
illustrates a state in which the light conversion filter 151 is
disposed in a central portion A of the light concentrator 110.
However, the light conversion filter 151 may be disposed at an
entrance B of the light concentrator 110 or at an exit C of the
light concentrator 110, that is, in the vicinity of the light
reception region C of the optical property measurement unit
140.
[0086] FIGS. 13A and 13B are diagrams illustrating examples of the
light conversion filter which may be used in this embodiment of the
present invention. Referring to FIG. 13A, a light conversion filter
150 may include a transparent substrate 150a such as glass, quartz,
or plastic and a phosphor layer 150b which is uniformly applied on
the transparent substrate 150a. Referring to FIG. 13B, a phosphor
plate or phosphor film 150' may be used as the above-described
light conversion filter. The phosphor layer 150b or the phosphor
plate or phosphor film 150' maybe formed of phosphor-containing
resin. The phosphor plate or phosphor film 150' maybe prepared by
the following process. For example, phosphor powder particles may
be dispersed in a transparent resin solvent and then cured into a
plate or film form.
[0087] The light conversion filters 150 and 150' may be used as the
light conversion filter 151 of the optical property evaluation
apparatus 100 according to the embodiment of the present invention.
For example, when the LED chip 10 mounted in the bare LED package
50 to be evaluated is a blue LED chip, the phosphor used in the
light conversion filters 150 and 150' may be a yellow phosphor
which converts blue light into yellow light. Furthermore, when the
LED chip 10 inside the bare LED package 50 is a blue LED chip, a
mixture of a red phosphor and a green phosphor may be used in the
light conversion filters 150 and 150'. When the LED chip 10 inside
the bare LED package 50 is a UV LED chip, a mixture of a red
phosphor, a green phosphor, and a blue phosphor may be used in the
light conversion filters 150 and 150'. The phosphors used in the
light conversion filters may include various phosphors such as a
garnet-based phosphor, a silicate-based phosphor, a nitride-based
phosphor, a sulfide-based phosphor, a halogen compound-based
phosphor, an aluminate-based phosphor, and an oxide-based phosphor.
In addition, various shapes, combinations, and compositions of
phosphors capable of realizing white light may be used as the light
conversion filters.
[0088] FIG. 14 is a schematic view of an apparatus for evaluating
the optical properties of an LED according to another embodiment of
the present invention. The optical property evaluation apparatus
according to the embodiment of the present invention includes an
integrating sphere 111 as a light concentrator which guides light
emitted from a bare LED package 50 or white light emitted from a
light conversion filter to a light reception region of an optical
property measurement unit 140, instead of the above-described
barrel-type light concentrator 12 (refer to FIG. 12). The
integrating sphere 111 includes an inner wall having a reflecting
surface capable of reflecting light. The integrating sphere 111 has
an exit for transferring light to the light reception region of the
optical property measurement unit 140.
[0089] Referring to FIG. 14, the light emitted from the bare LED
package 50, for example, blue light or UV light, is reflected by
the integrating sphere 111 and concentrated in the light reception
region of the optical property measurement unit 140. The light
conversion filter 140 is installed in the vicinity of the light
reception region of the optical property measurement unit 140. The
light conversion filter 140 converts the light concentrated on the
light reception region into a different wavelength of light to emit
white light. The white light obtained through the light conversion
filter 151 enters the spectrometer of the optical property
measurement unit 140 through an optical cable, for example, and the
chromaticity of the white light obtained through the light
conversion filter 151 is measured. The other components such as the
voltage application unit 115 and the functions thereof are the same
as those of the above-described embodiment (refer to FIG. 12).
[0090] FIG. 15 is a schematic view of an apparatus for evaluating
the optical properties of an LED according to another embodiment of
the present invention. In this embodiment of the present invention,
the integrating sphere 111 is used to concentrate light on the
light reception region of the optical property measurement unit
140, as in the embodiment of FIG. 14. In this embodiment, however,
the light conversion filter 151 converting the wavelength of light
emitted from the bare package 50 is disposed adjacent to the light
emission surface of the bare LED package 50. Referring to FIG. 15,
the light conversion filter 151 may be disposed at an entrance
opening of the integrating sphere 111 for introducing the light
emitted from the bare LED package 50 into the integrating sphere
111. Therefore, the white light emitted through the light
conversion filter 151 is concentrated by the integrating sphere
111, and enters the light reception region of the optical property
measurement unit to measure the chromaticity of the white light.
The other components and the functions thereof are the same as
those of the above-described embodiment.
[0091] FIG. 16 is a diagram illustrating an apparatus for
evaluating the optical properties of an LED according to another
embodiment of the present invention. Referring to FIG. 16, the
optical property evaluation apparatus according to the embodiment
of the present invention includes a bar-type light concentrator 112
having a narrow internal space as a light concentration unit for
guiding light emitted from the bare LED package 50 or the light
emitted from the light conversion filter 151 into the light
reception region of the optical property measurement unit 140,
instead of the integrating sphere or the barrel-type light
concentrator. The light emitted from the bare LED package 50 is
converted by the light conversion filter 151, and white light is
emitted from the light conversion filter 151. The optical property
measurement unit 140 measures the chromaticity of the white light.
The light conversion filter 151 may be disposed at various
positions inside the bar-type light concentrator 112.
[0092] The optical property evaluation apparatuses 100, 200, 200',
and 300 according to the above-described embodiments of the present
invention may be used to measure the chromaticity of the bare LED
package in the white chromaticity region. The measured white
chromaticity may be compared with the chromaticity of a white LED
device which has been manufactured by dispensing
phosphor-containing resin to the LED chip 10 inside the bare LED
package 50. Through the comparison, it is possible to establish or
set the correlation between the chromaticity of the white light
obtained through the light conversion filter in the operation of
evaluating the optical properties of the bare LED package and the
chromaticity of the white LED device which actually has been
manufactured by dispensing phosphor-containing resin to the LED
chip 10 mounted on the bare LED package 50. The established
correlation may be used for calculating a mixing ratio of
phosphor-containing resin which is to be applied to the LED chip 10
mounted on the bare LED package 50 to manufacture white LED devices
within the target chromaticity range.
[0093] FIG. 17 is a diagram showing a process of evaluating the
optical properties of a white LED device 70 which actually has been
manufactured by dispensing phosphor-containing resin to the LED
chip 10. The white LED device 70 maybe manufactured by the
following process. First, the LED chip 10, for example, a blue LED
chip is die-bonded to a package body 20, and wire bonding is
performed to manufacture a bare LED package. Then,
phosphor-containing resin 30, for example, yellow
phosphor-containing resin, is dispensed around the LED chip 10 and
then cured. In this case, the phosphor-containing resin 30 may be
dispensed to a reflecting cup of the package body 20 to seal the
LED chip 10. Before the phosphor-containing resin is dispensed, the
chromaticity of the bare LED package is measured by the
above-described optical property evaluation apparatus 100, 100',
200', or 300. The chromaticity of white light emitted from the
manufactured white LED device 70 may be measured by a typical
optical property measurement apparatus for a white LED device. The
white light emitted from the white LED device 70 may be transferred
to a measurement unit (not shown) through a light reception unit
210 and an optical cable 220 of the optical property measurement
apparatus to measure the chromaticity of the white light. The
chromaticity of the white light of the white LED device 70 to which
the phosphor-containing resin has been dispensed may be compared
with the chromaticity of the white light (emitted from the light
conversion filter) which is measured by the optical property
evaluation apparatus 100, 200, 200', or 300, in order to set the
correction data between the chromaticities.
[0094] FIGS. 18A and 18B show the spectrum and chromaticity of the
white light obtained from the light conversion filter 151 in the
optical property evaluation operation for the bare LED package. The
chromaticity is represented by a chromaticity of the CIE 1931
chromaticity system. FIGS. 19A and 19B show the spectrum and
chromaticity of the white light emitted from the white LED device
manufactured by applying phosphor-containing resin to the LED chip
mounted on the bare LED package having the properties of FIGS. 18A
and 18B. The phosphor-containing resin within the white LED device
is prepared at a well-known mixing ratio. A sufficient number of
LED chip samples and well-known mixing ratios may be used to
compare and analyze the chromaticity of the white light obtained
through the light conversion filter and the chromaticity of the
white LED device. Then, it is possible to establish and set the
correlation between the chromaticity of the white light obtained
from the light conversion filter in the chip probing operation and
the chromaticity of the white light obtained from the white LED
device, with respect to various mixing ratios. In FIGS. 18B and
19B, ranks depending on the chromaticities may be classified into
several regions. Based on the rank classification, it is possible
to establish the correlation between the chromaticity rank of the
white light emitted from the light conversion filter and the
chromaticity rank of the white light emitted from the white LED
device. At this time, the mean or median value of a proper number
of chromaticities corresponding to each rank may be set as a
representative value of the rank.
[0095] FIG. 20 is a flow chart explaining a method for evaluating
the optical properties of an LED chip according to another
embodiment of the present invention. The optical property
evaluation method may be performed by using the optical property
evaluation apparatuses 100, 100', 200', and 300 according to the
above-described embodiments of the present invention.
[0096] Referring to FIG. 20, light emitted from a bare LED package
50 which is to be evaluated is converted by the light conversion
filter 151, and white light is emitted from the light conversion
filter 151 (S11). The white light emitted from the light conversion
filter 151 enters the light reception region of the optical
property measurement unit 140 to measure the chromaticity of the
white light (S12). The light emitted from the bare LED package 50
or the white light emitted from the light conversion filter 151 may
be guided to the light reception region of the optical property
measurement unit 140 through the light concentrator such as the
integrating sphere, the barrel-type light concentrator, or the
bar-type light concentrator.
[0097] The above-described optical property evaluation method may
be utilized to manufacture white LED devices at a high production
yield and productivity. In particular, the optical property
evaluation method may be used for manufacturing white LED devices
satisfying a target chromaticity at a high yield.
[0098] FIG. 21 is a flow chart explaining a method for evaluating
the optical properties of an LED according to another embodiment of
the present invention. The optical property evaluation method may
be performed by using the optical property evaluation apparatuses
100, 100', 200', and 300 according to the above-described
embodiments of the present invention, excluding the light
conversion filter 151.
[0099] Referring to FIG. 21, when a driving voltage is applied to a
bare LED package 50 which is to be evaluated, the LED package bare
package 50 emits light, for example, blue light or UV light (S21).
The light (non-white light) emitted from the bare LED package 50 is
received to measure the chromaticity of the light (S22). During the
chromaticity measurement, the above-described barrel-type or
bar-type light concentrator or the integrating sphere may be used
to concentrate light on the light reception region of the optical
property measurement unit 140. In this embodiment, although the
chromaticity of the light emitted from the bare LED package 50 is
measured without a light conversion filter, the measured
chromaticity of the bare LED package is not always identical to the
chromaticity of light emitted from the LED chip without the bare
package. The chromaticity of the LED chip measured by using a chip
prober is not a chromaticity obtained by reflecting package
elements such as a package body, a lead frame, and a bonding wire,
but the chromaticity of the bare LED package obtained in the
embodiment of FIG. 21 may be a chromaticity obtained by reflecting
at least some of the package elements excluding phosphor-containing
resin. For example, when the bare LED package 50 includes a package
body, a lead frame, and a bonding wire, the chromaticity of the
bare LED package may be obtained by reflecting the effects caused
by the package elements excluding the phosphor-containing resin.
Furthermore, when the bonding wire is omitted as in the flip-chip
bonding operation or before the bonding wire is formed, the
chromaticity of the bare LED package may be obtained by reflecting
the effects caused by the package body and the lead frame.
[0100] Although a plurality of white LED devices are manufactured
by applying phosphor-containing resin prepared at the same mixing
ratio to a plurality of LED chips having the same chromaticity, the
plurality of white LED devices may have considerable chromaticity
distribution due to the deviation between the package elements.
However, the chromaticity of the bare LED package measured
according to the method of FIG. 21 is obtained by reflecting the
effects caused by at least some of package elements such as a
package body, a lead frame, and a bonding wire, excluding
phosphor-containing resin. Therefore, white LED devices
manufactured by applying phosphor-containing resin prepared at the
same mixing ratio to bare LED packages having the same chromaticity
may exhibit reduced chromaticity distribution.
[0101] The optical property evaluation methods of FIGS. 20 and 21
may not only be used in a method for manufacturing a white LED
device, but may also be utilized for analyzing and investigating
the cause of the chromaticity distribution of the white LED
devices. For example, the chromaticity measured in operation S12 or
S22 and the chromaticity of the white LED device which has been
manufactured may be compared, or the wavelengths, outputs, and
luminances of the LED chip and the white LED device may be compared
to analyze the cause of the chromaticity distribution.
[0102] FIG. 22 is a flow chart explaining a method for
manufacturing a white LED device according to another embodiment of
the present invention. Referring to FIG. 22, a bare LED package is
prepared (S101). The bare LED package may include a blue LED chip
or a UV LED chip. Next, the chromaticity of white light is measured
in accordance with the optical property evaluation method using the
light conversion filter (refer to FIG. 20) (S102). In the
chromaticity measurement operation S102, the chromaticity of the
white light obtained by converting light emitted from the bare LED
package through the light conversion filter is measured.
[0103] Then, the above-described correlation between the
chromaticities, that is, the preset correlation between the
chromaticity of the white light emitted from the light conversion
filter and the chromaticity of the white light emitted from the
white LED device is used to calculate a mixing ratio of
phosphor-containing resin which is to be applied to the bare
package to realize a target chromaticity, from the chromaticity
measured in operation S102 (S103). Subsequently,
phosphor-containing resin prepared at the calculated mixing ratio
is dispensed around the LED chip of the bare LED package to
manufacture a white LED device (S104). When the above-described
method for manufacturing a white LED device is used, it is possible
to more accurately calculate the mixing ratio of
phosphor-containing resin required for realizing the target
chromaticity. Accordingly, the production yield of white LED
devices satisfying the target chromaticity increases, and
productivity thereof is improved.
[0104] FIG. 23 is a flow chart explaining a method for
manufacturing a white LED device according to another embodiment of
the present invention. In this embodiment, the chromaticity of
light emitted from a bare LED package is measured without using a
light conversion filter, and a mixing ratio of phosphor-containing
resin is calculated depending on the measured chromaticity.
[0105] Referring to FIG. 23, a bare LED package is prepared (S201).
Next, the chromaticity of light emitted from the bare LED package
is measured in accordance with the method of FIG. 21 (S202). As
described above, the chromaticity of the bare LED package may be
considered to be a chromaticity obtained by reflecting the effects
of package elements such as a package body, a lead frame, and a
bonding wire.
[0106] Subsequently, based on the correlation between the
chromaticity (non-white color) of the bare LED package and the
chromaticity (white) of the white LED device manufactured by
dispensing phosphor-containing resin to the bare LED package, a
mixing ratio of phosphor-containing resin for realizing a target
chromaticity is calculated from the chromaticity of the bare LED
package measured in operation S202 (S203). Then, the
phosphor-containing resin prepared at the calculated mixing ratio
is dispensed around the LED chip of the bare LED package to
manufacture a white LED device (S204). When the method for
manufacturing a white LED device is used, it is possible to reduce
the chromaticity distribution of white LED devices caused by such
factors as the optical properties of LED chips, the shapes of lead
frames, and the positions of the LED chips. Therefore, the
production yield and productivity of white LED devices satisfying
the target chromaticity may be improved.
[0107] In the above-described embodiments, it has been described
that white light is emitted from the light conversion filter 150,
150, or 151. Furthermore, the method for manufacturing the white
LED device which emits white light by mixing monochromatic light
emitted from the LED chip and light emitted from the phosphors has
been described. However, the embodiments of the present invention
are not limited only to a case in which white light is emitted by
the light conversion filter or the white LED device is
manufactured. The embodiments of the present invention may be
applied to a case in which a non-white LED device is manufactured
or the optical properties of a bare LED package to be applied to
the non-white LED device are measured.
[0108] For example, a light conversion filter may be used to
convert red light emitted from a bare LED package having a red LED
chip mounted thereon into a different wavelength of light, and the
converted light and the red light may be mixed to finally emit
purple light as the mixed light. As the chromaticity of a specific
color of light other than the white light emitted from the light
conversion filter is measured, it is possible to evaluate the
optical properties of LED chips used in the specific color LED
devices. Accordingly, it is possible to reduce a chromaticity
distribution of the specific color LED devices.
[0109] In the above-described embodiments of the present invention,
the chromaticity of a specific color LED device such as the white
LED device manufactured by dispensing phosphor-containing resin to
the bare LED package may be optimized in accordance with the target
chromaticity.
[0110] Furthermore, since the correlation between the
chromaticities may be used to accurately calculate the mixing ratio
of phosphor-containing resin for realizing the target chromaticity,
it is possible to omit a dispensing process which is previously
performed on separate LED samples. Accordingly, the chromaticity
distribution of final specific color LED devices is reduced, and
the production yield and productivity thereof increases.
Furthermore, the optical property evaluation apparatus and method
may be used to effectively analyze the cause of the chromaticity
distribution of the specific color LED devices.
[0111] While the present invention has been shown and described in
connection with the exemplary embodiments, it will be apparent to
those skilled in the art that modifications and variations can be
made without departing from the spirit and scope of the invention
as defined by the appended claims.
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