US007960819B2
`
`(12) United States Patent
`Loh et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,960,819 B2
`Jun. 14, 2011
`
`(54) LEADFRAME-BASED PACKAGES FOR
`SOLID STATE EMITTING DEVICES
`
`(75) Inventors: Ban P. Loh, Durham, NC (US); Bernd
`Keller, Santa Barbara, CA (US);
`Nicholas W. Medendorp, Jr., Raleigh,
`NC (US)
`
`(73) Assignee: Cree, Inc., Durham, NC (US)
`(*) Notice:
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 65 days.
`
`(21) Appl. No.: 11/486,244
`(22) Filed:
`Jul. 13, 2006
`(65)
`Prior Publication Data
`US 2008/O121921 A1
`May 29, 2008
`(51) Int. Cl.
`(2006.01)
`HOIL 23/2495
`(52) U.S. Cl. ................... 257/676; 257/99; 257/E23.031
`(58) Field of Classification Search
`257/98
`257/99. 100, 676. E33 057 E33 058E33 072.
`257/E33 073. 666. 79 684 796 s 675 712.
`•
`- s 2 57,713 71, 720 E23 031
`See application file for complete search histo
`p
`ry.
`pp
`References Cited
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`(56)
`
`U.S. PATENT DOCUMENTS
`5,748,658 A
`5, 1998 Nakanishi et all
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`6, 1998 Lee
`6,376,902 B1
`4/2002 Arndt
`6,455,356 B1* 9/2002 Glenn et al. .................. 438.123
`S. R: g38 As
`6,680.49 B2* /2004 Shishi etal
`6,716,673 B2
`4/2004 Waitlet al.
`... 257/99
`6,747.293 B2 * 6/2004 Nitta et al.
`7,034,382 B2 * 4/2006 Palmteer et al. .............. 257,676
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`257/98
`
`2.9SR. $38, SE,
`Oberts et al.
`7,282,785 B2 10/2007 Yoshida
`2001/0000622 A1* 5/2001 Reeh et al. ...................... 257/98
`2002/0004251 A1
`1/2002 Roberts et al.
`2002/0163001 A1* 11/2002 Shaddock ....................... 257/79
`(Continued)
`
`CN
`
`FOREIGN PATENT DOCUMENTS
`1148637 A
`4f1997
`(Continued)
`OTHER PUBLICATIONS
`SnapLED 150 Technical Data DS08, Lumileds Lighting, LLC, Oct.
`11, 2004, pp. 1-6.
`
`(Continued)
`Primary Examiner — Evan Pert
`Assistant Examiner — Selim Ahmed
`(74) Attorney, Agent, or Firm — Myers Bigel Sibley &
`Sajovec
`(57)
`ABSTRACT
`A modular package for a light emitting device includes a
`leadframe having a top Surface and including a central region
`having a bottom Surface and having a first thickness between
`the top surface of the leadframe and the bottom surface of the
`central region. The leadframe may further include an electri
`cal lead extending away from the central region. The electri
`cal lead has a bottom Surface and has a second thickness from
`the top surface of the leadframe to the bottom surface of the
`electrical lead. The second thickness may be less than the first
`thickness. The package further includes a package body on
`the leadframe Surrounding the central region and exposing the
`bottom surface of the central region. The package body may
`beat least partially provided beneath the bottom surface of the
`lead and adjacent the bottom surface of the central region.
`Methods of forming modular packages and leadframes are
`also disclosed.
`
`16 Claims, 6 Drawing Sheets
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`260
`\ 240
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`23 NL
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`2
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`
`
`
`
`232
`
`NS
`
`
`
`
`
`204
`
`224
`
`2OOb
`
`226 230b
`
`2
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`202
`
`
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`2O2b
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`
`
`224
`226
`
`2OO
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`Nichia Exhibit 1006
`Page 1
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`

`

`US 7,960.819 B2
`Page 2
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`U.S. PATENT DOCUMENTS
`2004/0041222 A1
`3f2004 Loh ............................... 257/433
`2004/OO79957 A1
`4/2004 Andrews et al.
`2004/0080026 A1* 4/2004 Minamio et al. .............. 257,666
`2004/O126913 A1
`7, 2004 Loh
`2005, OO77623 A1* 4, 2005 Roberts et al. .....
`2005/O189626
`A1* 9, 2005 Xiaochun et al. ..
`2005.0218421
`A1* 10, 2005 Andrews et al. ...
`2005.0218489
`A1* 10, 2005 Satou et al. .............
`2005/0269587
`A1 12/2005 Loh et al.
`A1* 6/2006 Negley et al. ...........
`2006/O124953
`2006/0223238
`A1* 10, 2006 Koh et al. ...............
`
`257,724
`257,666
`257/100
`257,678
`
`.
`
`.
`
`.
`
`. 257/99
`438.123
`
`
`
`.
`
`.
`
`.
`
`CN
`CN
`JP
`JP
`
`FOREIGN PATENT DOCUMENTS
`16381.58 A
`7/2005
`1808713(A)
`T 2006
`2000-252323
`9, 2000
`2005-197369
`7/2005
`
`OTHER PUBLICATIONS
`
`Luxeone Star power light source Technical Datasheet DS23,
`Lumileds Lighting, LLC, Mar. 2006, pp. 1-18.
`Declaration of Gerald Negley under 37 C.F.R.S 1.132, dated Aug. 21.
`2009.
`Declaration of Charles Swoboda under 37 C.F.R.S 1.132, dated Aug.
`21, 2009.
`First Office Action for corresponding Chinese Patent Application No.
`200710142165.2 dated Mar. 24, 2010, 16 pages.
`Translation of First Office Action for Chinese Patent Application No.
`200810003832.3 dated Sep. 14, 2010.
`Translation of Second Chinese Office Action for corresponding Chi
`nese Application No. 200710142165.2 mailed Mar. 4, 2011.
`
`* cited by examiner
`
`Nichia Exhibit 1006
`Page 2
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`

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`U.S. Patent
`
`Jun. 14, 2011
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`Sheet 1 of 6
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`US 7,960,819 B2
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`15B
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`FIG. 1A
`PRIOR ART
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`
`
`FIGURE 1B
`PRIOR ART
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`Nichia Exhibit 1006
`Page 3
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`U.S. Patent
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`Jun. 14, 2011
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`Sheet 2 of 6
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`US 7,960,819 B2
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`104.
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`102a
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`102
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`FIGURE 2A
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`102a
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`124
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`106
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`
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`124a 100a
`V Va
`I-12
`2%),
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`104
`102 104b.
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`106b 102C
`102b
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`FIGURE 2B
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`100
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`112 114
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`106
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`severy SNAS
`2\R. Ziit
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`II
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`S
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`104
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`116
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`102
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`FIGURE 2C
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`Nichia Exhibit 1006
`Page 4
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`U.S. Patent
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`Jun. 14, 2011
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`Sheet 3 of 6
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`US 7,960,819 B2
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`106
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`104
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`FIGURE 3A
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`160 N
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`106
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`NR
`NL
`YNN SZ-S
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`104
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`106b
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`2
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`100
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`104b.
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`FIGURE 3B
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`Nichia Exhibit 1006
`Page 5
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`U.S. Patent
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`Jun. 14, 2011
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`Sheet 4 of 6
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`US 7,960,819 B2
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`100'
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`106
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`315 y
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`= 104
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`102"
`
`FIGURE 4A
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`1OO
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`
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`124
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`--N KS
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`102
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`FIGURE 4B
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`Nichia Exhibit 1006
`Page 6
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`

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`U.S. Patent
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`Jun. 14, 2011
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`Sheet 5 of 6
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`US 7,960,819 B2
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`260
`N 240
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`N
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`6. N y) 232
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`NS
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`204
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`226
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`202
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`202
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`202b
`FIGURE 5
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`206
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`200b
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`226 230b
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`FIGURE 6
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`Nichia Exhibit 1006
`Page 7
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`

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`U.S. Patent
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`Jun. 14, 2011
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`Sheet 6 of 6
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`US 7,960,819 B2
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`FIGURE 7
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`340
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`335
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`236
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`234
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`ON 232
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`1
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`S
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`360
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`344
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`204
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`226
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`224
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`200
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`FIGURE 8
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`Nichia Exhibit 1006
`Page 8
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`

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`US 7,960,819 B2
`
`1.
`LEADFRAME-BASED PACKAGES FOR
`SOLID STATE EMITTING DEVICES
`
`FIELD OF THE INVENTION
`
`2
`heat is extracted out of the package through the leads 25A,
`25B, the package may still have a thermal resistance that
`limits the performance of the device.
`
`SUMMARY
`
`This invention relates to Solid state light emitting devices,
`and more particularly to packages for Solid state light emit
`ting devices and methods of forming packages for Solid State
`light emitting devices.
`
`10
`
`BACKGROUND
`
`35
`
`It is known to mount Solid State light sources. Such as
`semiconductor light emitting devices, in packages that may
`provide protection, color selection, focusing, and the like, for 15
`light emitted by the light emitting device. A solid State light
`emitting device may be, for example, an organic or inorganic
`light emitting diode (“LED). Some packages for light emit
`ting diodes are described in U.S. Pre-grant Publication Nos.
`2004/0079957, 2004/0126913, and 2005/0269587 which are 20
`assigned to the assignee of the present invention, and which
`are incorporated herein by reference as if set forth fully
`herein.
`Packages as described in the above referenced publications
`may be suitable for high power, Solid State illumination appli- 25
`cations. However, notwithstanding the advances described
`therein, there remains a need for improved packages in which
`multiple LEDs may be mounted. In particular, in Some gen
`eral lighting applications it may be desirable for an LED
`package to include multiple LEDs emitting in different 30
`regions of the visible spectrum. Light emitted by the LEDs
`may combine to produce a desired intensity and/or color of
`light, Such as white light or any other desired color. In that
`case, it may be desirable for the LEDs in the package to be
`mounted relatively closely together.
`A typical leadframe-based LED package includes electri
`cal leads, contacts or traces for electrically connecting the
`LED package to an external circuit. In a typical LED package
`10 illustrated in FIG. 1A, an LED chip 12 is mounted on a
`reflective cup 13 by means of a solder bond or conductive 40
`epoxy. One or more wirebonds 11 connect the ohmic contacts
`of the LED chip 12 to leads 15A and/or 15B, which may be
`attached to or integral with the reflective cup 13. The reflec
`tive cup 13 may be filled with an encapsulant material 16
`containing a wavelength conversion material Such as a phos- 45
`phor. Light emitted by the LED at a first wavelength may be
`absorbed by the phosphor, which may responsively emit light
`at a second wavelength. The entire assembly is then encap
`sulated in a clear protective resin 14, which may be molded in
`the shape of a lens to collimate the light emitted from the LED 50
`chip 12. However, heat retention may be an issue for a pack
`age such as the package 10 shown in FIG. 1A, since it may be
`difficult to extract heat through the leads 15A, 15B.
`A conventional Surface-mountable leadframe-based pack
`age 20 is illustrated in FIG. 1B. The package 20 includes an 55
`LED chip 22 mounted on a reflective cup 23. One or more
`wirebonds 21 connect the ohmic contacts of the LED chip 22
`to leads 25A and/or 25B, which may be attached to or integral
`with the reflective cup 23. A clear protective resin 24 is cast
`around the assembly. The reflective cup 23 may be formed by 60
`stamping a thin sheet of metal when the leadframe is formed.
`Stamping the reflective cup 23 may result in thinning of the
`base and/or sidewalls of the cup 23. However, since heat may
`be extracted through the leads 25A, 25B, the thickness of the
`cup 23 may not limit the thermal performance of the package 65
`20. The package 23 may have more and/or larger leads 25A,
`25B compared to the package 10 of FIG. 1A. However, since
`
`A modular package for a light emitting device according to
`some embodiments of the invention includes a leadframe
`having a top surface and including a central region having a
`bottom Surface and having a first thickness between the top
`surface of the leadframe and the bottom surface of the central
`region. The leadframe may further include an electrical lead
`extending laterally away from the central region. The electri
`cal lead has a bottom Surface and has a second thickness from
`the top surface of the leadframe to the bottom surface of the
`electrical lead adjacent the central region. The second thick
`ness may be less than the first thickness. The package further
`includes a package body on the leadframe Surrounding the
`central region and exposing the bottom Surface of the central
`region. The package body may be at least partially provided
`beneath the bottom surface of the lead and adjacent the bot
`tom Surface of the central region.
`The central region may include a die mounting region, and
`the electrical lead may be isolated from the die mounting
`region. The package body may include upper sidewalls that
`define an optical cavity above the die mounting region.
`The upper sidewalls may include oblique inner Surfaces
`that define a reflector cup surrounding the die mounting
`region.
`The modular package may further include an encapsulant
`above the reflector cup, the encapsulant defining a lens above
`the reflector cup.
`In some embodiments, the modular package may further
`include a circumferential rim Surrounding the die mounting
`region, and a lens on the circumferential rim. The modular
`package may further include a circumferential moat Sur
`rounding the circumferential rim.
`The package body may define an optical cavity above the
`top Surface of the die mounting pad, and at least a portion of
`the package body may extend through the leadframe.
`The central region may include a reflector cup therein
`including oblique sidewalls extending from an upper corner
`of the reflector cup to a base of the reflector cup. A third
`thickness between the base of the reflector cup and the bottom
`Surface of the central region may be greater than the second
`thickness. A width of the central region may be greater than a
`width of the base of the reflector cup. Furthermore, a width of
`the central region may be greater than or equal to a width of
`the reflector cup at the upper corner thereof.
`The modular package may further include a Submount on
`the base of the reflector cup, a solid state light emitting device
`on the Submount, and a wirebond connection from the Solid
`state light emitting device to the electrical lead.
`The package body may include upper sidewalls that define
`an optical cavity above the reflector cup. The reflector cup
`may include a first reflector cup and the upper sidewalls
`include oblique inner surfaces that define a second reflector
`cup surrounding the first reflector cup. The modular package
`may further include a encapsulant above the reflector cup, the
`encapsulant forming a lens above the reflector cup. The
`modular package may further include a circumferential rim
`Surrounding the reflector cup and a lens on the circumferen
`tial rim. The modular package may further include a circum
`ferential moat Surrounding the circumferential rim.
`The package body has a bottom Surface that may be Sub
`stantially coplanar with the bottom surface of the central
`region of the leadframe.
`
`Nichia Exhibit 1006
`Page 9
`
`

`

`US 7,960,819 B2
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`5
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`10
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`15
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`25
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`35
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`3
`The modular package may further include a plurality of
`electrical leads, and the central region may include a plurality
`of die mounting pads that are electrically connected to respec
`tive ones of the plurality of electrical leads and that are con
`figured to receive a light emitting device.
`The leadframe may have a thickness less than 30 mils. In
`Some embodiments, the leadframe may have a thickness of
`about 15 mils.
`A leadframe for a package for a light emitting device
`according to Some embodiments of the invention includes a
`top Surface and a central region having a bottom Surface and
`having a first thickness between the top surface of the lead
`frame and the bottom surface of the central region. The lead
`frame further includes an electrical lead extending laterally
`away from the central region. The electrical lead has a bottom
`Surface and a second thickness from the top Surface of the
`leadframe to the bottom surface of the electrical lead adjacent
`the central region. The second thickness may be less than the
`first thickness.
`The central region may include a reflector cup therein
`including oblique sidewalls extending from an upper corner
`of the reflector cup to a base of the reflector cup. A third
`thickness between the base of the reflector cup and the bottom
`Surface of the central region may be greater than the second
`thickness. A width of the central region may be greater than a
`width of the base of the reflector cup. A width of the central
`region may be greater than or equal to a width of the reflector
`cup at the upper corner thereof.
`Some embodiments of the invention provide methods of
`30
`forming a package for a solid state light emitting device. The
`methods include providing a leadframe having a top surface
`and including a central region having a bottom surface and
`having a first thickness between the top surface of the lead
`frame and the bottom Surface of the central region and includ
`ing an electrical lead extending laterally away from the cen
`tral region, the electrical lead having a bottom Surface and a
`second thickness from the top surface of the leadframe to the
`bottom surface of the electrical lead adjacent the central
`region. The second thickness may be less than the first thick
`ness. The methods further include forming a package body on
`the leadframe Surrounding the central region and exposing the
`bottom surface of the central region. The package body may
`be at least partially formed beneath the bottom surface of the
`lead and adjacent the bottom Surface of the central region.
`The central region may include a die mounting region, and
`the package body may include upper sidewalls that define an
`optical cavity above the die mounting region and that include
`oblique inner Surfaces that define a reflector cup Surrounding
`the die mounting region, and the methods may further include
`dispensing an encapsulant in the reflector cup. The encapsu
`lant may form a lens above the reflector cup. The methods
`may further include positioning a lens above the reflector cup.
`The package body may further include a circumferential
`rim Surrounding the die mounting region, and positioning the
`lens above the reflector cup may include bringing the lens into
`contact with the circumferential rim.
`The central region may include a reflector cup therein
`including oblique sidewalls extending from an upper corner
`of the reflector cup to a base of the reflector cup. A third
`thickness between the base of the reflector cup and the bottom
`Surface of the central region may be greater than the second
`thickness. The methods may further include positioning a
`Submount on the base of the reflector cup, positioning a solid
`state light emitting device on the Submount, and forming a
`wirebond connection from the Solid state light emitting
`device to the electrical lead.
`
`4
`Forming the package body may include forming the pack
`age body to expose a bottom Surface of the central region of
`the leadframe.
`The methods may further include dispensing an encapsu
`lant into the reflector cup. The encapsulant may form a lens
`above the reflector cup.
`The package body may further include a circumferential
`rim Surrounding the die mounting region, and the methods
`may further include bringing a lens into contact with the
`circumferential rim.
`Methods of forming a leadframe for a solid state light
`emitting package according to Some embodiments of the
`invention include providing a leadframe blank having a top
`Surface, a central region having a bottom surface and having
`a first thickness between the top surface of the leadframe
`blank and the bottom surface of the central region, and a
`portion extending laterally away from the central region, the
`portion extending away from the central region having a
`bottom surface and a second thickness adjacent the central
`region from the top surface of the leadframe to the bottom
`Surface of the portion extending away from the central region,
`and stamping a reflector cup into the central region. The
`second thickness may be less than the first thickness.
`Stamping the reflector cup into the central region may
`include bringing a stamp including a protrusion having a
`shape defining a desired shape of the reflector cup into contact
`with the upper surface of the leadframe blank above the
`central region, and applying Sufficient energy to the stamp to
`impress an image of the protrusion into the central region of
`the leadframe blank.
`The methods may further include trimming excess material
`Squeezed out while stamping the reflector cup from the lead
`frame blank.
`The reflector cup may include oblique sidewalls extending
`from an upper corner of the reflector cup to a base of the
`reflector cup, and a third thickness between the base of the
`reflector cup and the bottom surface of the central region may
`be greater than the second thickness. A width of the central
`region may be greater than a width of the base of the reflector
`cup. A width of the central region may be greater than or equal
`to a width of the reflector cup at the upper corner thereof.
`Methods of forming a leadframe for a solid state light
`emitting package according to further embodiments of the
`invention include providing a leadframe blank having a top
`Surface and a bottom surface, and selectively etching the
`leadframe blank to provide a first region having a bottom
`Surface and having a first thickness between the top Surface of
`the leadframe blank and the bottom surface of the region, and
`a second region having a bottom Surface and a second thick
`ness from the top surface of the leadframe to the bottom
`Surface of the second region. The second thickness may be
`less than the first thickness. The first thickness may be less
`than 30 mils. The first thickness may be about 15 mils. Selec
`tively etching the leadframe blank may include selectively
`etching the leadframe blank to form a recess in the leadframe
`having a depth of about 10 mils.
`
`40
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`45
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`50
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`55
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`60
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`65
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`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The accompanying drawings, which are included to pro
`vide a further understanding of the invention and are incor
`porated in and constitute a part of this application, illustrate
`certain embodiment(s) of the invention. In the drawings:
`FIGS. 1A and 1B are cross-sectional side views illustrating
`conventional packages for light emitting devices.
`
`Nichia Exhibit 1006
`Page 10
`
`

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`US 7,960,819 B2
`
`5
`FIG. 2A is a top view and FIGS. 2B and 2C are a cross
`sectional side views illustrating a leadframe for one or more
`light emitting devices according to some embodiments of the
`present invention;
`FIG.3A is a side view and FIG.3B is a cross sectional side
`view of a package for one or more light emitting devices
`according to some embodiments of the invention;
`FIGS. 4A and 4B are schematic diagrams illustrating the
`formation of a lead frame according to some embodiments of
`the invention;
`FIG. 5 is a cross sectional side view of a package for one or
`more light emitting devices according to further embodi
`ments of the invention;
`FIG. 6 is a top view of a leadframe configured for use in a
`package according to embodiments of the invention;
`FIG. 7 is a cutaway view of a package for one or more light
`emitting devices according to embodiments of the invention;
`and
`FIG. 8 is a cross sectional side view of a package for one or
`more light emitting devices according to still further embodi
`ments of the invention.
`
`10
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`15
`
`6
`Unless otherwise defined, all terms (including technical
`and Scientific terms) used herein have the same meaning as
`commonly understood by one of ordinary skill in the art to
`which this invention belongs. It will be further understood
`that terms used herein should be interpreted as having a
`meaning that is consistent with their meaning in the context of
`this specification and the relevant art and will not be inter
`preted in an idealized or overly formal sense unless expressly
`so defined herein.
`Embodiments of the invention are described herein with
`reference to cross-section illustrations that are schematic
`illustrations of idealized embodiments (and intermediate
`structures) of the invention. The thickness of layers and
`regions in the drawings may be exaggerated for clarity. Addi
`tionally, variations from the shapes of the illustrations as a
`result, for example, of manufacturing techniques and/or tol
`erances, are to be expected. Thus, embodiments of the inven
`tion should not be construed as limited to the particular shapes
`of regions illustrated herein but are to include deviations in
`shapes that result, for example, from manufacturing.
`As used herein, the term semiconductor light emitting
`device may include a light emitting diode, laser diode and/or
`other semiconductor device which includes one or more
`semiconductor layers, which may include silicon, silicon car
`bide, gallium nitride and/or other semiconductor materials, a
`Substrate which may include Sapphire, silicon, silicon carbide
`and/or other microelectronic Substrates, and one or more con
`tact 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 may also be provided. The design and fabrica
`tion of semiconductor light emitting devices are well known
`to those having skill in the art and need not be described in
`detail herein.
`For example, the semiconductor light emitting devices
`packaged in accordance with embodiments of the invention
`may be gallium nitride-based LEDs or lasers fabricated on a
`silicon carbide Substrate Such as those devices manufactured
`and sold by Cree, Inc. of Durham, N.C. The LEDs and/or
`lasers may be configured to operate Such that light emission
`occurs through the substrate in a so-called “flip chip' orien
`tation.
`Referring now to FIGS. 2A-2C, a leadframe 100 according
`to some embodiments of the invention is illustrated. FIG. 2A
`is a top view of the leadframe 100, while FIGS. 2B and 2C are
`cross sections taken along line A-A of FIG. 2A. The lead
`frame 100 includes a central region 102 and a plurality of
`leads 104, 106 extending away from the central region 102.
`The electrical leads 104, 106 may be electrically isolated
`from one another and/or from the central region 102 of the
`leadframe 100. The leads may be arranged such that leads of
`opposite polarity type (e.g. anodes or cathodes) are provided
`on opposite sides of the leadframe 100, which may facilitate
`the connection of packages using the leadframes 100 in
`series.
`As shown in FIG. 2A, the leadframe 100 further has an
`upper surface 100a. The central region 102 of the leadframe
`100 has a substantially flat lower surface 102b that is spaced
`apart from lower surfaces 104b. 104c of the leads 104,106 by
`sidewalls 102c. The central region 102 has a first thickness
`(i.e. the distance between the upper surface 100a of the lead
`frame 100 and the lower surface 102b of the central region
`102), and the electrical leads 104, 106 have a second thick
`ness (i.e. the distance between the upper surface 100a of the
`leadframe 100 and the lower surface 104b, 106b of the respec
`tive leads 104,106) that is less than the first thickness.
`
`DETAILED DESCRIPTION OF EMBODIMENTS
`OF THE INVENTION
`
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`30
`
`The present invention now will be described more fully
`hereinafter with reference to the accompanying drawings, in
`which embodiments of the invention are shown. This inven
`tion may, however, be embodied in many different 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
`convey the 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 numbers refer to like
`elements throughout.
`It will be understood that when an element such as a layer,
`region or Substrate is referred to as being “on” or extending
`“onto' another element, it can be directly on or extend
`directly onto the other element or intervening elements may
`40
`also be present. In contrast, when an element is referred to as
`being “directly on' or extending “directly onto' another ele
`ment, there are no intervening elements present. It will also be
`understood that when an element is referred to as being “con
`nected' or “coupled to another element, it can be directly
`connected or coupled to the other element or intervening
`elements may be present. In contrast, when an element is
`referred to as being “directly connected or “directly
`coupled to another element, there are no intervening ele
`ments present.
`Relative terms such as “below” or “above” or “upper” or
`“lower” or “horizontal” or “lateral” or “vertical” may be used
`herein to describe a relationship of one element, layer or
`region to another element, layer or region as illustrated in the
`figures. It will be understood that these terms are intended to
`encompass different orientations of the device in addition to
`the orientation depicted in the figures.
`It will be understood that, although the terms first, second,
`etc. may be used herein to describe various elements, com
`ponents, regions, layers and/or sections, these elements, com
`60
`ponents, regions, layers and/or sections should not be limited
`by these terms. These terms are only used to distinguish one
`element, component, region, layer or section from 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.
`
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`Nichia Exhibit 1006
`Page 11
`
`

`

`US 7,960,819 B2
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`10
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`7
`A reflector cup 120 is formed in the central region 102. The
`reflector cup 124 includes an oblique sidewall that extends
`from the upper surface 100a of the leadframe 100 to a base
`124b located within the central region 102. The reflector cup
`124 may have an arbitrary peripheral shape. However, in the
`embodiments illustrated in FIGS. 2A-2C, the reflector cup
`124 has a generally circular peripheral shape. Thus, the
`oblique sidewall of the reflector cup 124 may form a generally
`circular upper lip 124a where the reflector cup 124 intersects
`the upper surface 100a of the leadframe 100. The sidewall of
`the reflector cup 124 shown in FIGS. 2A-C has the shape of a
`conic section (e.g. a frustum). However, the sidewall of the
`reflector cup 124 may form other shapes, for example, a solid
`parabolic section.
`The base 124b of the reflector cup 124 has a diameter that
`is less than a width of the central region 102 (i.e. a distance
`between the sidewalls 102c of the central region 102). Fur
`thermore, the upper lip 124a of the reflector cup 124 has a
`diameter that may be less than or equal to the width of the
`central region 102. Moreover, the thickness of the central
`region 102 between the base 124b of the reflector cup 124 and
`the lower surface 102b of the central region 102 may be
`thicker than electrical leads 104,106. As will be explained in
`greater detail below, a package for a solid state light emitting
`device may dissipate heat through the central region 102 of
`the leadframe 100, rather than through the leads 104, 106.
`Thus, the relative physical dimensions of the central region
`102 may improve the heat dissipation properties of the pack
`age by reducing the thermal resistance of the package.
`Thermal resistance is inversely proportional to the Surface
`area through which heat is conducted. That is, thermal resis
`tance is defined by the equation
`(1)
`R=L/kA
`where k is the coefficient of thermal conductivity, L is the
`length of the material through which heat is to be dissipated,
`and A represents the area through which heat is to be dissi
`pated. Thus, when heat is dissipated through a large Surface
`such as the lower surface 102b of the central region 102, the
`thermal resistance of the package may be lowered. Further
`40
`more, while according to equation (1) the greater thickness of
`the central region 102 may increase the thermal resistance of
`the package somewhat, the thickness of the central region 102
`may permit heat to spread more before it is extracted from the
`package. Since heat in an LED package is generated in a
`relatively small area (i.e. the area of the light emitting devices
`114), it may be desirable to increase the thickness of the
`central region 102 in order to take better advantage of the
`relatively large surface area of the central region 102.
`Referring to FIG. 2C, a submount 116 including a plurality
`of solid state light emitting devices 114 is mounted within the
`reflector cup 124 on the base 124b thereof. The submount 116
`may include a nonconductive material Such as aluminum
`nitride, silicon carbide and/or chemical vapor deposited
`(CVD) diamond on which a plurality of electrical traces (not
`shown) may be formed. The thermal conductivity of alumi
`num nitride and silicon carbide is about 400W/MK, while the
`thermal conductivity of CVD diamond is about 800 W/MK.
`The thickness of the submount 116 may be from about 300 to
`about 600 um, although other thicknesses may be used. A
`60
`plurality of wirebond connections 112 are made between the
`submount 116 and the devices 114 on one hand and respective
`ones of the electrical leads 104,106 on the other hand.
`A package 160 including the leadframe 100 is illustrated in
`FIGS. 3A and 3B, which are side and cross sectional side
`views, respectively, of a package 160 for one or more light
`emitting devices. Referring to FIGS. 3A and 3B, the package
`
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`8
`160 includes a molded package body 130 surrounding the
`leadframe 100 and a lens 140 mounted over the central region
`102 of the leadframe 100. The electrical leads 104,106 extend
`from sides of the package body 130. Other optical features,
`Such as reflectors, diffusers, etc., may be provided instead of
`or in addition to the lens 140.
`The package body 130 may be formed, for example, of
`thermoplastic by transfer or injection molding, around the
`leadframe 100. The thermoplastic may include a liquid crys
`tal polymer such as a Vectra(R) series polymers A130 and/or
`S1