`
`346
`
`B2
`
`US007279
`
`United States Patent
`(12)
`(10) Patent No.:
`US 7,279,346 B2
`Andrewset al.
`(45) Date of Patent:
`Oct. 9, 2007
`
`
`(54) METHOD FOR PACKAGING A LIGHT
`EMITTING DEVICE BY ONE DISPENSE
`THEN CURE STEP FOLLOWED BY
`ANOTHER
`
`5,027,168 A
`5,043,716 A
`5,210,051 A
`5,338,944 A
`
`6/1991 Edmond oo... 357/17
`8/1991 Latz etal. ove 340/782
`vee 437/107
`5/1993 Carter, Jn.
`.....
`
`8/1994 Edmond et al... 257/76
`
`(75)
`
`Inventors: Peter Andrews, Durham, NC (US);
`Thomas G. Coleman,Pittsboro, NC
`(US); James Ibbetson, Goleta, CA
`(US); Michael Leung, Port Hueneme,
`CA (US); Gerald H. Negley, Carrboro,
`NC (US); Erie Tarsa, Goleta, CA (US)
`
`(73) Assignee: Cree, Inc., Durham, NC (US)
`
`(Continued)
`.
`-
`_
`i
`
`FOREIGN PATENT DOCUMENTS
`101 09 349
`9/2002
`
`DE
`
`(*) Notice:
`
`Subject to any disclaimer, the termof this
`patent is extended or adjusted under 35
`USC. 154(b) by 42 days.
`
`Continued
`(Continued)
`
`OTHER PUBLICATIONS
`
`(21) Appl. No.: 11/044,126
`
`(22)
`
`Filed:
`
`Jan. 27, 2005
`
`(65)
`
`Prior Publication Data
`US 2005/0218421 Al
`Oct. 6, 2005
`
`Related U.S. Application Data
`(60) Provisional application No. 60/557,924,filed on Mar.
`31, 2004.
`Int. CL.
`HOLL 33/00
`
`2006.01
`
`(51)
`
`)
`(
`(52) US. Ch.ee 438/27, 257/E33.059
`k
`:
`oe
`:
`:
`J
`(58) Field of Classificationseareh257)98.100. oeron
`tication
`f at
`file
`1
`h his
`.
`See application
`file
`for complete search
`history.
`References Cited
`U.S. PATENT DOCUMENTS
`
`(56)
`
`3,805,347 A *
`3,875,456 A
`4,822,536 A *
`4,918,497 A
`4,966,862 A
`
`4/1974 Collins et al. we. 445/24
`4/1975 Kano et al. oo. 313/501
`4/1989 Voinis et al. 264/446
`. SS7/17
`4/1990 Edmond ...
`
`10/1990 Edmond. oo... 437/100
`
`International Search Report and Written Opinion of the Interna-
`tional Searching Authority for corresponding PCT application No.
`PC1/US2005/010034, mailed Feb, 22, 2006.
`
`(Continued)
`Primary Examiner—Sara Crane
`Assistant Examiner—Andrew O Arena
`(74) Attorney, Agent, or Firm—Myers Pigel Sibley &
`Sajovec
`(57)
`
`ABSTRACT
`
`Methodsofpackaging a semiconductorlight emitting device
`“
`:
`:
`:
`:
`:
`positioned ina reflective cavity are provided. Afirst quantity
`ofencapsulant material is dispensed into the reflective cavity
`including the light emitting device therein and the first
`quantity of encapsulant in the reflective cavity is cured. A
`second quantity of encapsulant material is dispensed onto
`the cured first quantity of encapsulant material. A lens is
`positioned in the reflective cavity on the dispensed second
`quantity of encapsulant material. The dispensed second
`quantity of encapsulant material is cured to attach the lens in
`the reflective cavity.
`
`18 Claims, 10 Drawing Sheets
`
`{
`
`)
`Begin
`——_t.
`/
`Bispenga First Quantity]
`ofEneassuiant
`|
`Materiat 1o Form First
`Convex Menisess
`
`4300
`
` Position Lene in
`
`EncapsulantMateria}
`
`
`ure First Quannyor 1,
`Zneaplant Material
`
`t
`Guanstyef
`1
`|
`| Dispense Second /
`‘Encapsulant Rieterin|
`'
`1
`Convex
`Meniscus
`
`Uf ee
`I
`
`
`Reflective Cavity
`tr. asa
`
`Cure Dispensed
`SecondQuantity of
`
`ye
`
`1320
`
`Nichia Exhibit 1008
`Page 1
`
`Nichia Exhibit 1008
`Page 1
`
`

`

`US 7,279,346 B2
`Page 2
`
`U.S. PATENT DOCUMENTS
`
`5,393,993
`5,416,342
`5,523,589
`5,631,190
`5,739,554
`5,912,477
`5,959,316
`6,120,600
`6,187,606
`6,201,262
`6,604,135
`6,610,563
`6,635,363
`6,642,652
`6,744,077
`6,746,295
`6,747,406
`6,917,057
`2001/0030326
`2002/0057056
`2002/0079837
`2002/0123164
`2002/0163001
`2003/0006418
`
`Al
`
`2/1995
`5/1995
`6/1996
`5/1997
`4/1998
`6/1999
`9/1999
`9/2000
`2/2001
`3/2001
`8/2003
`8/2003
`10/2003
`11/2003
`6/2004
`6/2004
`6/2004
`7/2005
`10/2001
`5/2002
`6/2002
`9/2002
`11/2002
`1/2003
`
`
`
`Edmondetal.
`....
`Edmond ct al.
`.
`Edmond ct al.
`Negley ............
`Ldimond et al.
`.
`Negley .........
`Lowery ........
`¢
`Edmondetal.
`Edmond et alo oe. 438/46
`. 257/77
`Edmond et al.
`....
`
`Edmond et al... 437/22
`Waitl et al.
`Duclos et al. we 428/690
`Collins, II] et al.
`........ 313/512
`Trottier et al. we. 257/103
`w. 445/24
`SOL .eesecessecerseeves
`
`........ 313/512
`Bortscheller et al.
`Stokes et al. wwe 257/98
`Reeh et al. wee 257/98
`Okazaki
`Okazaki
`Slater, Jr. et al. oe... 438/39
`Shaddock ........
`257/79
`
`Emerson et al. w...00...... 257/79
`
`7/2003 Brunneretal.
`2003/0141510 Al
`11/2003 Sorg occ eeeeee: 445/24
`2003/0211804 Al
`
`{2004 LOW vescesscesssesessseeees 257/433
`2004/0041222 Al
`3/2004 Slater, Jr. et al. cece 257/79
`2004/0056260 Al
`
` FOREIGN PATENT DOCUMENTS
`
`EP
`IP
`JP
`JP
`JP
`JP
`JP
`Wo
`WO
`
`1 187 226
`08032120
`09027643
`10-65220
`10-190065
`3604298 B
`2005-197369 A
`WO 01/15242
`WO 2004/068594
`
`3/2002
`2/1996
`1/1997
`3/1998
`7/1998
`12/2004
`7/2005
`3/2001
`3/2004
`
`OTHER PUBLICATIONS
`
`Inlernalional Search Report and Written Opinion of the Interna-
`Uional Searching Authorily for International Patent Applicalion No.
`PCT/US2005/00779 mailed on Feb. 28, 2006.
`International Search Report and Written Opinion of the Interna-
`tional Searching Authority for International Patent Application No.
`PCT/US2005/009778 mailed on Mar. 8, 2006.
`
`* cited by examiner
`
`Nichia Exhibit 1008
`Page 2
`
`Nichia Exhibit 1008
`Page 2
`
`

`

`U.S. Patent
`
`Oct. 9, 2007
`
`Sheet 1 of 10
`
`US 7,279,346 B2
`
`«s— 100
`
`102
`
`
`Nichia Exhibit 1008
`Page 3
`
`Nichia Exhibit 1008
`Page 3
`
`

`

`U.S. Patent
`
`Oct. 9, 2007
`
`Sheet 2 of 10
`
`US 7,279,346 B2
`
`200 N |
`
`115d
`
`«100
`
`
`Nichia Exhibit 1008
`Page 4
`
`Nichia Exhibit 1008
`Page 4
`
`

`

`U.S. Patent
`
`Oct. 9, 2007
`
`Sheet 3 of 10
`
`US 7,279,346 B2
`
`104 —~
`
`105
`
`Y
`
`FIG. 4B
`
`FIG. 5B
`
`FIG. 5A
`
`Nichia Exhibit 1008
`Page 5
`
`Nichia Exhibit 1008
`Page 5
`
`

`

`FIG. 6
`
`
`
`a
`
`
`
`NNI
`
`FIG. 7
`
`Nichia Exhibit 1008
`Page 6
`
`
`
`
`

`

`U.S. Patent
`
`Oct. 9, 2007
`
`Sheet 5 of 10
`
`
`
`US 7,279,346 B2
`
`Nichia Exhibit 1008
`Page 7
`
`Nichia Exhibit 1008
`Page 7
`
`

`

`U.S. Patent
`
`Oct. 9, 2007
`
`Sheet 6 of 10
`
`US 7,279,346 B2
`
`
`FIG. 9C
`
`{0B
`
`Nichia Exhibit 1008
`Page 8
`
`Nichia Exhibit 1008
`Page 8
`
`

`

`U.S. Patent
`
`Oct. 9, 2007
`
`Sheet 7 of 10
`
`US 7,279,346 B2
`
`FIG. 10A
`
`IG. 10C
`
`/ F
`
`/ 10C
`
`Nichia Exhibit 1008
`Page 9
`
`Nichia Exhibit 1008
`Page 9
`
`

`

`U.S. Patent
`
`Oct. 9, 2007
`
`Sheet 8 of 10
`
`US 7,279,346 B2
`
`¥
`
`1100
`
`Mountlight emitting
`
`device
`Dispense FirstQuantitySo
`
`
`1120
`
`of Encapsulant
`Material
`
`1130
`
`+140
`
`
`Dispense Second
`Quantity of
`
`
`Encapsulant Material
`|
`
`
`
`
`
`Cure Dispensed
`Encapsulant Materiai
`
`FIG. 11
`
`Nichia Exhibit 1008
`Page 10
`
`Nichia Exhibit 1008
`Page 10
`
`

`

`U.S. Patent
`
`Oct. 9, 2007
`
`Sheet 9 of 10
`
`US 7,279,346 B2
`
`1200
`
`’
`
`Mountlightemitting Lo
`device
`
`
`
`4210
`
`
`Dispense Encapsulant
`Material to form
`
`Convex Meniscus
`
`
`
`
`
`v
`
`1220
`
`Cure Dispensed
`Encapsulant Material
`
`
`
`FIG. 12
`
`Nichia Exhibit 1008
`Page 11
`
`Nichia Exhibit 1008
`Page 11
`
`

`

`U.S. Patent
`
`Oct. 9, 2007
`
`Sheet 10 of 10
`
`US 7,279,346 B2
`
`Dispense First Quantity
`of Encapsulant
`Material to Form First
`Convex Meniscus
`
`Cure First Quantity of
`Encapsulant Material
`
`
`
`
`
`Dispense Second
`Quantity of
`Encapsulant Material to
`Form Second Convex
`Meniscus
`
`
`
`Position Lens in
`
`
`Reflective Cavity
`
`
`4320
`
`1330
`
`Cure Dispensed
`Second Quantity of
`
`Encapsulant Material
`
`End
`
`FIG. 13
`
`Nichia Exhibit 1008
`Page 12
`
`Nichia Exhibit 1008
`Page 12
`
`

`

`US 7,279,346 B2
`
`1
`METHOD FOR PACKAGING A LIGHT
`EMITTING DEVICE BY ONE DISPENSE
`THEN CURE STEP FOLLOWED BY
`ANOTHER
`
`RELATED APPLICATION
`
`This application claims the benefit of and priority to U.S.
`Provisional Patent Application No. 60/557,924, entitled
`“Methods for Packaging a light I'mitting Device,” filed
`Mar. 31, 2004, the disclosure of which is hereby incorpo-
`rated herein byreference as if set forth in its entirety.
`
`D
`
`BACKGROUND OF THE INVENTION
`
`
`
`
`
`i)D
`
`weD
`
`35
`
`This invention relates to semiconductor light emitting
`devices and fabricating methods therefore, and more par-
`ticularly to packaging and packaging methods for semicon-
`ductor light emitting devices.
`It
`is known to provide semiconductor light emitting
`device type light sources in packages
`that may provide
`protection, color selection, focusing and the like for light
`emitted by the light emitting device. For example, the light
`emilling device may be a light emitting diode (“LED”).
`Various problems may be encountered during packaging of
`
`a power LED for use as a light source. Examples of such
`possible problems will be described with reference to the
`cross-sectionalillustrations of a power LED in FIGS. 1 and
`2. As shown in FIGS. 1 and 2, a power LED package 100
`generally includes a substrate member 102 on which a light
`emitting device 103 is mounted. The light emitting device
`103 may,
`for example,
`include an LED chip/submount
`assembly 1034 mounted to the substrate member 102 and an
`
`LED 103a positioned on the LED chip/submount assembly
`103. The substrate member 102 may include traces or metal
`leads for connecting the package 100 to external circuitry.
`The substrate 102 mayalso act as a heatsink to conduct heat
`away from the LED 103 during operation.
`Areflector, such as the reflector cup 104, may be mounted
`on the substrate 102 and surround the light emitting device
`103. The reflector cup 104 illustrated in FIG. 1 includes an
`angled or sloped lower sidewall 106 for reflecting light
`generated by the LED 103 upwardly and awayfrom the LED
`package 100. The illustrated reflector cup 104 also includes
`upwardly-extending walls 105 that mayact as a channel for
`holding a lens 120 in the LED package 100 and a horizontal
`shoulder portion 108.
`Asillustrated in FIG. 1, after the light emitting device 103
`is mounted on the substrate 102, an encapsulant material
`w2
`112, such as liquid silicone gel, is dispensed into an interior 5
`reflective cavity 115 of the reflector cup 104. The interior
`reflective cavity 115 illustrated in FIG. 1 has a bottom
`surface defined by the substrate 102 to provide a closed
`cavity capable of retaining a liquid encapsulant material 112
`therein. As further shown in FIG. 1, when the encapsulant
`material 112 is dispensed into the cavity 115, it may wick up
`the interior side of the sidewall 105 of the reflector cup 104,
`forming the illustrated concave meniscus.
`As shownin FIG. 2, a lens 120 may then be placed into
`the reflective cavity 115 in contact with the encapsulant
`material 112. When the lens 120 is placed in the cavity 115,
`the liquid encapsulant material 112 may be displaced and
`move through the gap 117 between the lens 120 and the
`sidewall 105. The encapsulant may, thus, be moved out onto
`the uppersurface ofthe lens 120 and/or upper surfacesofthe
`sidewall 105 of the reflector cup 104. This movement, which
`may bereferred to as squeeze-out, is generally undesirable
`
`2
`for a numberof reasons. In the depicted package arrange-
`ment, the lens will sit on a lower shelf if the encapsulant is
`not cured in a domed meniscus shapepriorto the lens attach
`step. This may cause the lens to not float during thermal
`cycling and fail via delamination of encapsulation to other
`surfaces or via cohesive failure within the delamination,
`both of which mayaffect the light output. The encapsulant
`material or gel is generally sticky and mayinterfere with
`automated processing tools used to manufacture the parts.
`Moreover, the gel may interfere with light output from the
`lens 120, for example, by changing the light distribution
`pattern and/or by blocking portions of the lens 120. The
`sticky gel mayalso attract dust, dirt and/or other contami-
`
`nants that could block or reduce light output from the LED
`package 100. The gel may also change the shape of the
`effective lens, which may modify the emitted light pattern/
`beam shape.
`the package 100 is
`After placement of the lens 120,
`typically heat-cured, which causes the encapsulant material
`112 to solidify and adhereto the lens 120. ‘lhe lens 120 may,
`thus, be held in place by the cured encapsulant material 112.
`However, encapsulant materials having a slight shrinkage
`factor with curing, such as a silicone gel, generally tend to
`* contract during the heat curing process. In addition, the
`coefficient of thermal expansion (CTE) effect generally
`causes higher floating of the lens at elevated temperatures.
`During cool-down,parts have a tendency to delaminate. As
`the illustrated volume of encapsulant beneath the lens 120
`shown in FIG. 2 is relatively large, this contraction may
`cause the encapsulant material 112 to delaminate (pull away)
`fromportions of the package 100, including the light emit-
`ting device 103, a surface of the substrate 102, the sidewalls
`105 of the reflector cup 104 and/or the lens 120 during the
`curing process. The delamination may significantly affect
`optical performance, particularly when the delamination is
`from the die, where it may cause total internal reflection.
`‘This contraction maycreate gaps or voids 113 betweenthe
`encapsulant material 112 and the light emitting device 103,
`lens 120, and/or reflector cup 104. Tri-axial stresses in the
`encapsulant material 112 mayalso cause cohesive tears 113'
`in the encapsulant material 112. These gaps 113 and/ortears
`113' may substantially reduce the amountoflight emitted by
`the light emitting device package 100. The contraction may
`also pull out air pockets from crevices(i.e, reflector) or from
`under devices (i.e., die/submount), which maytheninterfere
`with optical cavity performance.
`During operation of the lamp, large amounts of heat may
`be generated by the light emitting device 103. Muchofthe
`heat may be dissipated by the substrate 102 andthereflector
`cup 104, cach of which mayact as a heatsink for the package
`100. However, the temperature of the package 100 maystill
`
`increase significantly during operation. Encapsulant mate-
`rials 112, suchas silicone gels, typically have high coefti-
`cients of thermal expansion. As a result, when the package
`100 heats up, the encapsulant material 112 may expand. As
`the lens 120 is mounted within a channel defined by the
`sidewalls 105 of the reflector cup 104, the lens 120 may
`travel up and down within the sidewalls 105 as the encap-
`sulant material 112 expands and contracts. Expansion of the
`encapsulant material 112 mayextrude the encapsulant into
`spaces or out of the cavity such that, when cooled, it may not
`move back into the cavity. This could cause delamination,
`5 vaids, higher triaxial stresses and/or the like, which may
`result in less robust light emitting devices. Such lens move-
`ment
`is further described, for example,
`in United States
`
`40
`
`;
`
`55
`
`Qa
`0
`
`Nichia Exhibit 1008
`Page 13
`
`Nichia Exhibit 1008
`Page 13
`
`

`

`US 7,279,346 B2
`
`3
`Patent Application Pub. No. 2004/0041222. The sidewalls
`105 may also help protect the lens 120 from mechanical
`shock and stress.
`
`
`
`SUMMARY OF THE INVENTION
`
`4
`quantity of encapsulant material may be substantially free of
`phosphor. In other words, each dispense maybe of a material
`with or without phosphor.
`In other embodiments of the present invention, position-
`ing the lens includes advancing the lens into the reflective
`cavity until it contacts the cured first quantity of encapsulant
` Embodiments of the present invention provide methods of
`material. A first quantity of encapsulant material may be
`dispensedthat is sufficient to establish a desired position for
`packaging a semiconductorlight emitting device, where the
`the lens in the reflective cavity. The light emitting device
`light emitting device may be mounted on a bottom surface
`maybe a light emitting diode (1.1/1).
`of a reflective cavity. A first quantity of encapsulant material
`In further embodiments of the present invention, methods
`is dispensed into the reflective cavity including the light
`of packaging a semiconductorlight emitting device include
`emitting device and the first quantity of encapsulant in the
`providing the light emitting device on a bottom surface of a
`reflective cavity is cured. A second quantity of encapsulant
`reflective cavity. The light emitting device has a height
`material is dispensed onto the cured first quantity of encap-
`relative to the bottom surface. A first quantity of encapsulant
`sulant material. A lens is positioned in the reflective cavity
`material is dispensed into the reflective cavity including the
`on the dispensed second quantity of encapsulant material.
`light emitting device. The first quantity is sufficient to wet
`The dispensed second quantity of encapsulant material is
`the light emitting device without filling the reflective cavity
`cured to attach the lens in the reflective cavity.
`to a level exceeding the height of the light emitting device.
`In other embodiments ofthe present invention, dispensing
`A second quantity of encapsulant material may be dispensed
`a first quantity of encapsulant material into the reflective
`onto the first quantity of encapsulant material. The dispensed
`cavity including the light emitting device includes dispens-
`encapsulant material is cured.
`ing a first portion ofthefirst quantity of encapsulant material
`In other embodiments of the present invention, packaging
`into the reflective cavity including the light emitting device
`a semiconductorlight emitting device includes providing the
`and a secondportion. ‘lhe first portion 1s sufficient to wet the
`light emitting device on a bottom surface ofa reflective
`light emitting device withoutfilling the reflective cavity to
`cavity. A first quantity of encapsulant material is dispensed
`a level exceeding the height ofthe light emitting device. The
`into thereflective cavity including the light emitting device.
`second portion of the first quantity of encapsulant material
`The first quantity is sufficient to substantially cover the light
`is dispensed onto the first portion of the first quantity of
`emitting device without forming any air pockets in the
`encapsulant material.
`encapsulant material. A second quantity of encapsulant
`In further embodiments ofthe present invention, dispens-
`material maybe dispensed onto the first quantity of encap-
`ing a first quantity of encapsulant material into thereflective
`sulant material. The different dispenses may be ofdifferent
`cavity including the light emitting device includes dispens-
`materials having different viscosities or other properties. For
`ing a first portion ofthefirst quantity of encapsulant material
`example, different viscosities of material maybe selected for
`into the reflective cavity including the light emitting device
`wetting and/or meniscus formation purposes. ‘lhe dispensed
`and a second portion. Thefirst portion ofthe first quantity is
`encapsulant material is cured.
`sufficient to substantially cover the light emitting device
`In further embodiments of the present invention, packag-
`without forming anyair pockets in the encapsulant material.
`ing a semiconductor light emitting device includes dispens-
`The second portion of the first quantity of encapsulant
`ing a first quantity of encapsulant material havingafirst
`&D
`material
`is dispensed onto the first portion of the first
`index ofrefraction into a reflective cavity including the light
`quantity of encapsulant material. The second portion maybe
`emitting device. The first quantity of encapsulant material is
`about twice the first portion. The second quantity may be
`cured. A second quantity of encapsulant material
`is dis-
`about equal to thefirst portion of the first quantity. Thefirst
`pensed onto the cured first quantity of encapsulant material.
`portion may be sufficient to fill
`the reflective cavity to a
`The second quantity of encapsulant material has a second
`height of about 250 microns.
`index ofretraction, different from the first index ofrefrac-
`tion. The first and second index ofrefraction are selected to
`In other embodiments of the present invention, curing the
`first quantity of encapsulant material includes curing thefirst
`provide a buried lens in the reflective cavity. The second
`portion of the first quantity of encapsulant material before
`quantity of encapsulant material is cured to form the buried
`lens.
`dispensing the second portion of the first quantity of encap-
`sulant material. The first portion of the first quantity of ;
`encapsulant material may include a phosphorand the second
`portion of the first quantity of encapsulant material may be
`substantially free of phosphor.
`In further embodiments of the present invention, the light
`emitting device is mounted at about a midpomt ofthe
`reflective cavity. The encapsulant material may be dispensed
`at a point displaced from the midpoint towards a sidewall of
`the cavily so that the encapsulant material is not dispensed
`directly onto the light emitting device. Alternatively, the
`encapsulant material may be dispensed directly onto the
`light emitting device. Dispensing the encapsulant material
`may include forming a bead of the encapsulant material on
`an end of a dispenser and contacting the formed bead with
`the reflective cavity and/or the light emitting device to
`dispense the bead from the dispenser. The encapsulant
`material may bea silicone gel. The first quantity of encap-
`sulant material may include a phosphor and the second
`
`l'IGS. 1 and 2 are cross-sectional side viewsillustrating a
`conventional light emitting device package;
`FIGS.3A to 3C are cross-sectional side viewsillustrating
`methods of packaging a light emitting device according to
`some embodiments of the present invention;
`FIG. 4A is a top viewillustrating a light emitting device
`package suitable for use with some embodiments of the
`Qa
`q present invention;
`FIG.4Bis a cross-sectionalside view illustrating the light
`emitting device package of FIG. 4A;
`FIG. 5A is a top viewillustrating a light emitting device
`package according to some embodiments of the present
`invention;
`FIG.5Bis a cross-sectional side view illustrating the light
`emitting device package of FIG. 5A;
`
`D
`
`i)D
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`Nichia Exhibit 1008
`Page 14
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`Nichia Exhibit 1008
`Page 14
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`FIG. 6 is a cross-sectional side view illustrating a light
`emitting device package according to further embodiments
`of the present invention;
`FIG. 7 is a cross-sectional side view illustrating a light
`emitting device package according to other embodiments of
`the present invention;
`FIGS. 8A to 8C are cross-sectional side viewsillustrating
`methods of packaging a light emitting device according to
`further embodiments of the present invention;
`‘IGS. 9A to 9C are cross-sectional side viewsillustrating
`methods of packaging a light emitting device according to
`other embodiments of the present invention;
`FIGS. 10A to 10C are cross-sectional side views illus-
`trating methods of packaging a light emitting device accord-
`ing to yet further embodiments ofthe present invention;
`FIG. 11 is a flowchart illustrating operations for packag-
`ing a light emitting device according to some embodiments
`of the present invention;
`FIG. 12 is a flowchart illustrating operations for packag-
`ing a light emitting device according to some other embodi-
`ments of the present invention; and
`FIG. 13 is a flowchart illustrating operations for packag-
`ing a light emitting device according to yet further embodi-
`ments of the present invention.
`
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`
`DETAILED DESCRIPTION
`
`
`
`The present invention now will be described more fully
`hereinafter with reference lo the accompanying drawings, in
`which embodiments of the invention are shown. This inven-
`tion may, however, be embodied in manydifferent forms and
`should not be construed as limited to the embodiments set
`forth herein. Rather, these embodiments are provided so that
`this disclosure will be thorough and complete, and will fully
`conveythe scope of the invention to those skilled in the art.
`In the drawings, the size and relative sizes of layers and
`regions may be exaggerated for clarity. Like numbersrefer
`to like elements throughout.
`It will be understood that when an element suchasa layer,
`region or substrate is referred to as being “on” another
`element, it can be directly on the other element or interven-
`ing elements may also be present. It will be understood that
`if part of an element, such as a surface, is referred to as
`“inner,” it is farther from the outside of the device than other
`parts of the element. Furthermore, relative terms such as
`“beneath” or “overlies” may be used herein to describe a
`relationship of one layer or region to anotherlayer or region
`relative to a substrate or base layer as illustrated in the
`figures. It will be understood that these terms are mtended to
`encompass different orientations of the device in addition to
`the orientation depicted in the figures. Finally, the term
`“directly” meansthat there are no intervening elements. As
`used herein, the term “and/or” includes any and all combi-
`nations of one or more of the associated listed items.
`Tt will be understood that, although the termsfirst, second,
`etc. may be used herein to describe various elements,
`components, regions, layers and/or sections, these elements,
`components, regions, layers and/or sections should not be
`limited by these terms. These terms are onlyused to distin-
`guish one element, component, region, layer or section trom
`another region,
`layer or section. Thus, a first element,
`component, region, layer or section discussed below could
`be termed a second element, component, region, layer or
`section without departing from the teachings of the present
`invention.
`Various embodiments of the present invention for pack-
`aging a semiconductor light emitting device 103 will be
`
`US 7,279,346 B2
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`6
`described herein. As used herein, the term semiconductor
`light emitting device 103 mayinclude a light emitting diode,
`laser diode and/or other
`semiconductor device which
`includes one or more semiconductor layers, which may
`include silicon, silicon carbide, galliumnitride and/or other
`semiconductor materials, a substrate which may include
`sapphire, silicon, silicon carbide and/or other microelec-
`tronic substrates, and one or more contact layers which may
`include metal and/or other conductive layers.
`In some
`embodiments, ultraviolet, blue and/or green light emitting
`diodes (“LEDs”) may be provided. Red and/or amber LEDs
`mayalso be provided. The design and fabrication of semi-
`conductor light emitting devices 103 are well known to
`those having skill in the art and need not be described in
`detail herein.
`For example, the semiconductorlight emitting device 103
`
`maybe gallium nitride-based LEDsor lasers fabricated on
`a silicon carbide substrate such as those devices manufac-
`tured and sold by Cree, Inc. of Durham, N.C. The present
`invention maybesuitable for use with LEDs and/orlasers as
`described in U.S. Pat. Nos. 6,201,262; 6,187,606; 6,120,
`600; 5,912,477; 5,739,554; 5,631,190; 5,604,135; 5.523,
`589; 5,416,342; 5,393,993; 5,338,944; 5,210,051; 5,027,
`168; 5,027,168; 4,966,862 and/or 4,918,497, the disclosures
`of which are incorporated herein by reference as ifset forth
`fully herein. Other suitable LEDsand/orlasers are described
`in published U.S. Patent Publication No. US 2003/0006418
`Al entitled Group II] Nitride Based Light Emitting Diode
`Structures With a Quantum Well and Superlattice. Group III
`Nitride ]3ased Quantum Well Structures and Group III
`Nitride Based Superlattice Structures, published Jan. 9,
`2003, as well as published U.S. Patent Publication No. US
`2002/0123164 AJ entitled Light Emitting Diodes Including
`
`Modifi cations for Light Extraction and Manufacturing
`Methods ‘Therefor.
`l‘urthermore, phosphor coated [.1:)s,
`such as those described in U.S. application Ser. No. 10/659,
`241, entitled Phosphor-Coated Light Emitting Diodes
`Including, Tapered Sidewalls and Fabrication Methods
`Therefor, filed Sep. 9, 2003, the disclosure of which is
`incorporated by reference herein as if set forth fully, may
`also be suitable for use in embodiments of the present
`invention. The LEDs and/or lasers may be configured to
`operate such that light emission occurs through the sub-
`strate. In such embodiments, the substrate may be patterned
`so as to enhance light output of the devices as is described,
`for example, in the above-cited U.S. Patent Publication No.
`US 2002/0123164 Al.
`invention will now be
`Embodiments of the present
`described with reference to the various embodimentsillus-
`trated in FIGS. 3-11. More particularly, some embodiments
`of a double-cure encapsulation process for use in packaging
`a light emitting device 103 are illustrated in FIGS. 3A
`through 3C. Such a double cure encapsulauion process may
`reduce problems associated with shrinkage of encapsulant
`material during curing. As will be described herein. for some
`embodiments of the present
`invention,
`the double cure
`process mayinclude three dispense operations and two cure
`operations. However, it will be understood that moreor less
`dispense operations and cure operations may also be used in
`packaging the light emitting device in other embodiments of
`the present invention. As will also be further described
`herein, embodiments of the present invention also include a
`multi-dispense operation, leading to a first cure operation
`followed by another set of dispense and cure operations to
`attach a lens.
`Asillustrated in FIG. 3A, a first predetermined amount
`(quantity) of an encapsulant material, including two encap-
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`Page 15
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`US 7,279,346 B2
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`sulant material portions 112, 114 in the illustrated embodi-
`ments, is dispensed within the cavity 115. The encapsulant
`material 112, 114 may be, for example, a liquidsilicongel,
`an epoxyorthelike. The first portion 112 may be dispensed
`0 wet exposed surface portions of the light emitting device
`103, more particularly, the led chip/submount assembly 101
`of the light emitting device 103, and the substrate 102.
`Portions of the reflector cup 104 may also be wet by the
`initial dispense. In some embodiments of the present inven-
`ion, the quantity of encapsulant material dispensed as the
`first portion 112 is sufficient to wet the light emitting device
`103 without filling the reflective cavity to a level exceeding
`he height of the light emitting device 103. In some other
`embodimentsof the present invention, the quantity of encap-
`sulant material dispensed asthe first portion 112 is sufticient
`o substantially cover the light emitting device 103 without
`orming any air pockets in the encapsulant material 112.
`As shownin FIG. 3A, the light emitting device is posi-
`ioned at about a midpoint 1157 ofthe reflective cavity 115.
`The encapsulant material may be dispensed froma dispenser
`200 at a point 115d displaced from the midpoint 115mm
`owards a sidewall 105 ofthereflective cavity 115 so that the
`encapsulant material 112 is not dispensed directly onto the
`ight emitting device 103. Dispensing encapsulant material
`112 directly on the light emitting device 103 may cause
`rapping of bubbles as the encapsulant material 112 passes
`over the structure of the light emitting device 103 from
`above. However, in other embodimentsofthe present inven-
`ion, the encapsulant material 112 is dispensed on top of the
`ight emitting device 103 die in addition to or instead of an
`offset dispense. Dispensing the encapsulant material 112
`may include forming a bead of the encapsulant material 112
`onanend ofa dispenser 200 and contacting, the formed bead
`with thereflective cavity 115 and/or the light emitting device
`103 to dispense the bead from the dispenser.
`The viscosity and/or other properties of the material used
`for a dispense may be selected such that, for example,
`wetting occurs without bubble formation. In further embodi-
`ments of the present invention, coatings may be applied to
`surfaces contacted by the dispensed material to speed/retard
`the wetting rate. For example, using certain known cleaning
`proceduresthat leave microscopic residue, selected surfaces
`may be treated and, thus, used to engineer the dynamics of
`the wetting action.
`Due to the surface properties of the inner surface of the
`reflector cup 104 defining the cavity 115, of the light
`emitting device 103 and of the encapsulant material 112,
`dispensed encapsulant material 112, even when dispensed
`from a point 115d displaced from the midpoint 115m of the
`w2
`cavity 115, may flow within the cavity 115 in a mannerthat 5
`could still cause bubbles in the encapsulant material 112. In
`particular, the encapsulant material 112 is expected to move
`or “wick” more rapidly around the inner surface of the
`reflector cup 104 and the sidewalls of the light emitting
`device 103 faster than over the top ofthe light emitting 55
`device 103. As a result, a bubble could be trapped on a side
`of the cavity 115 opposite from the side where the encap-
`sulant material is dispensed when the side flowing encap-
`sulant material meets and then encapsulant material flows
`over the top of the light emitting device 103, thus being
`locally dispensed from above with no side outlet for air flow.
`Accordingly, the quantity of the first portion of dispensed
`encapsulant material 112 may be selected to reduce or
`prevent the risk of forming such bubbles. As such, as used
`herein, reference to “substantially” covering the light emit-
`