Filed on behalf of: Nichia Corp.
`
`Paper ____
`
`D(cid:68)(cid:87)(cid:72)(cid:3)(cid:73)(cid:76)(cid:79)(cid:72)d: June 1(cid:20), 2018
`
`By: Martin M. Zoltick, Lead Counsel
`Robert Parker, Back-up Counsel
`Jenny L. Colgate, Back-up Counsel
`Derek F. Dahlgren, Back-up Counsel
`Michael H. Jones, Back-up Counsel
`Mark T. Rawls, Back-up Counsel
`ROTHWELL, FIGG, ERNST & MANBECK, P.C.
`607 14th Street, N.W., Suite 800
`Washington, DC 20005
`Phone: 202-783-6040
`Facsimile: 202-783-6031
`
`UNITED STATES PATENT AND TRADEMARK OFFICE
`_______________
`
`BEFORE THE PATENT TRIAL AND APPEAL BOARD
`_______________
`
` VIZIO INC.,
`Petitioner,
`
`v.
`
`NICHIA CORP.,
`Patent Owner.
`_______________
`
`Case IPR2017-01608
`Patent 8,530,250
`_______________
`
`SECOND DECLARATION OF DR. E. FRED SCHUBERT
`
`NICHIA EXHIBIT 2031
`Vizio, Inc. v. Nichia Corp. Case
`IPR2018-00437
`
`EXHIBIT 2031 - IPR Page 1
`
`

`

`Filed on behalf of: Nichia Corp.
`
`Paper ____
`
`D(cid:68)(cid:87)(cid:72)(cid:3)(cid:73)(cid:76)(cid:79)(cid:72)d: June 1(cid:20), 2018
`
`By: Martin M. Zoltick, Lead Counsel
`Robert Parker, Back-up Counsel
`Jenny L. Colgate, Back-up Counsel
`Derek F. Dahlgren, Back-up Counsel
`Michael H. Jones, Back-up Counsel
`Mark T. Rawls, Back-up Counsel
`ROTHWELL, FIGG, ERNST & MANBECK, P.C.
`607 14th Street, N.W., Suite 800
`Washington, DC 20005
`Phone: 202-783-6040
`Facsimile: 202-783-6031
`
`UNITED STATES PATENT AND TRADEMARK OFFICE
`_______________
`
`BEFORE THE PATENT TRIAL AND APPEAL BOARD
`_______________
`
` VIZIO INC.,
`Petitioner,
`
`v.
`
`NICHIA CORP.,
`Patent Owner.
`_______________
`
`Case IPR2017-01608
`Patent 8,530,250
`_______________
`
`SECOND DECLARATION OF DR. E. FRED SCHUBERT
`
`(cid:49)(cid:44)(cid:38)(cid:43)(cid:44)(cid:36)(cid:3)(cid:40)(cid:59)(cid:43)(cid:44)(cid:37)(cid:44)(cid:55)(cid:3)(cid:21)(cid:19)(cid:22)(cid:19)
`(cid:57)(cid:76)(cid:93)(cid:76)(cid:82)(cid:15)(cid:3)(cid:44)(cid:81)(cid:70)(cid:17)(cid:3)(cid:89)(cid:17)(cid:3)(cid:49)(cid:76)(cid:70)(cid:75)(cid:76)(cid:68)(cid:3)(cid:38)(cid:82)(cid:85)(cid:83)(cid:17)
`(cid:38)(cid:68)(cid:86)(cid:72)(cid:3)(cid:44)(cid:51)(cid:53)(cid:21)(cid:19)(cid:20)(cid:26)(cid:16)(cid:19)(cid:20)(cid:25)(cid:19)(cid:27)
`
`EXHIBIT 2031 - IPR Page 2
`
`

`

`TABLE OF CONTENTS
`
`Schubert Declaration
`IPR2017-01608
`
`I(cid:1)
`
`Introduction .......................................................................................................... 1
`
`II(cid:1) Qualifications ....................................................................................................... 1
`
`III Materials considered ......................................................................................... 7
`
`IV(cid:1)
`
`Summary of opinions ....................................................................................... 7
`
`V(cid:1) Technology background ...................................................................................... 8
`
`A.
`
`LED device technology overview ...............................................................12
`
`1. LED device components: structure and function ........................................12
`
`B.
`
`LED packaging: integrating multiple design challenges ...........................17
`
`1. Electrical design challenges ........................................................................17
`
`2. Optical design challenges ............................................................................18
`
`3. Mechanical design challenges .....................................................................19
`
`4. Thermal design challenges ..........................................................................19
`
`5. Chemical and photochemical design challenges .........................................23
`
`6. Manufacturing challenges ...........................................................................25
`
`7. Competing considerations in LED packaging design .................................27
`
`C. Additional design challenges: size, cost, and manufacturing capacity ......29
`
`1. Size ..............................................................................................................30
`
`2. Cost ..............................................................................................................30
`
`3. High-throughput manufacturing capacity ...................................................32
`
`D. Other differences .........................................................................................39
`
`VI(cid:1) Definition of one of ordinary skill in the art ..................................................45
`
`VII(cid:1) Claim construction ..........................................................................................48
`
`VIII
`
`Prior art references ......................................................................................49
`
`A.
`
`Park ’697 .....................................................................................................49
`
`2
`
`EXHIBIT 2031 - IPR Page 3
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`

`

`Schubert Declaration
`IPR2017-01608
`
`B.(cid:1) Urasaki .........................................................................................................58(cid:1)
`
`C.(cid:1) Oshio ............................................................................................................59(cid:1)
`
`D.(cid:1)
`
`Park ’486 .....................................................................................................61(cid:1)
`
`IX(cid:1) The claims of the ’250 patent are not unpatentable .......................................64(cid:1)
`
`A.(cid:1) Claims 1 and 7 would not have been obvious in view of the cited
`references ..............................................................................................................66(cid:1)
`
`1.(cid:1) Park ‘697 fails to disclose, and would not have suggested, “transfer-
`molding a thermosetting resin … to form a resin-molded body” (claim element
`1[c]) and “cutting the resin-molded body and the plated lead frame along the at
`least one notch to form a resin package” (claim element 1[d]) .........................66(cid:1)
`
`2.(cid:1) Park ’486 does not remedy the deficiencies of Park ’697 ...........................93(cid:1)
`
`3.(cid:1) The Petition does not allege that the other cited references remedy the
`deficiencies of Park ’697 and Park ’486 (and they do not) .............................106(cid:1)
`
`B.(cid:1) Claims 17, 19, and 21 would not have been obvious in view of the cited
`references ............................................................................................................107(cid:1)
`
`1.(cid:1) Park ’697 does not disclose the specific plating requirements of claim 17
`107(cid:1)
`
`2.(cid:1) A POSITA would not have modified Park ’697 to have plating as claimed
`118(cid:1)
`
`3.(cid:1) Oshio does not remedy the deficiencies of Park ’697 ...............................126(cid:1)
`
`X(cid:1) Objective indicia support the nonobviousness of the challenged claims of the
`’250 patent ..............................................................................................................132(cid:1)
`
`Secondary considerations or objective indicia support a finding of
`A.(cid:1)
`nonobviousness ...................................................................................................132(cid:1)
`
`1.(cid:1) Commercial success ..................................................................................133(cid:1)
`
`2.(cid:1) Other secondary considerations ................................................................135(cid:1)
`
`B.(cid:1) Nichia’s products practice the claims of the ’250 Patent ..........................137(cid:1)
`
`1.(cid:1) Representative Nichia products .................................................................137(cid:1)
`
`2.(cid:1) Laboratory testing: IAL/TAEUS technical analysis reports ....................138(cid:1)
`
`3.(cid:1) Testimonial evidence .................................................................................140(cid:1)
`
`3
`
`EXHIBIT 2031 - IPR Page 4
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`

`

`Schubert Declaration
`IPR2017-01608
`
`C.(cid:1) Nichia’s 757 and 157 series products practice the independent claims of the
`’250 Patent ..........................................................................................................141(cid:1)
`
`1.(cid:1) Analysis for 757 product series .................................................................142(cid:1)
`
`2.(cid:1) Analysis for 157 product series .................................................................169(cid:1)
`
`XI(cid:1) Conclusion ....................................................................................................193(cid:1)
`
`4
`
`EXHIBIT 2031 - IPR Page 5
`
`

`

`these defects or otherwise motivate the skilled person to modify Park ’697 in the
`
`Schubert Declaration
`IPR2017-01608
`
`manner proposed by Petitioner.
`
`V TECHNOLOGY BACKGROUND
`
`21.
`
`The ’250 Patent relates to a fabrication process sequence for the
`
`packaging of light emitting diodes (“LEDs”). LEDs used in lighting applications
`
`are semiconductor devices made from inorganic (non-carbon-based) materials that
`
`produce light when electrical current flows through them. LEDs provide superior
`
`performance and unique benefits over conventional lighting sources (such as
`
`incandescent and fluorescent lighting sources). These unique benefits include their
`
`compact size, long lifespan, resistance to mechanical impact, lack of ultraviolet
`
`emissions, ultra-fast response times, and the ability to control the brightness and
`
`color of the emitted light.
`
`22.
`
`The long lifespan and durability of LEDs is one of their most
`
`significant advantages over conventional lighting sources. Unlike other light
`
`sources, LEDs typically do not completely “burn out” and stop emitting light
`
`altogether, but instead gradually deteriorate in brightness over time, by a process
`
`known as “lumen depreciation.” Thus, the useful lifespan of LEDs is typically
`
`measured in terms of the number of hours until the LED emits only 70 percent of
`
`its original light output. By this measure, well-designed LEDs often enjoy
`
`8
`
`EXHIBIT 2031 - IPR Page 6
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`

`

`Schubert Declaration
`IPR2017-01608
`
`lifespans on the order of 25,000 hours or longer. By comparison, a typical
`
`incandescent light bulb lasts only approximately 1,000 hours before completely
`
`burning out.
`
`23. LEDs also offer significantly higher energy efficiency and reduced
`
`power consumption relative to conventional lighting sources. LEDs therefore offer
`
`the potential for tremendous cost savings from reduced expenditures on energy for
`
`lighting. It is estimated that switching to SSL (Solid-State Lighting) could reduce
`
`national lighting energy use by 75 percent in 2035, saving 5.1 quadrillion BTUs1—
`
`nearly equal to the total annual energy consumed by 45 million U.S. homes.2
`
`24. LEDs are environmentally friendly, more so than conventional light
`
`sources. LED manufacturing avoids the use of toxic mercury that is required to
`
`manufacture fluorescent lighting products. Furthermore, the use of LEDs results in
`
`drastic reductions in the emission of carbon dioxide and sulfur dioxide (i.e. gases
`
`causing global warming and acid rain) into the environment.
`
`25. Finally, LEDs also offer a greater number of design and display
`
`options over conventional lighting products, including the following:
`
`• Greater design flexibility due to small size;
`
`
`
`(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1) (cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)
`
`1 British Thermal Unit (BTU) is an energy unit. 1 kWh is equal to 3412.14 BTUs.
`2 See http://energy.gov/eere/ssl/why-ssl.
`
`
`
`9
`
`EXHIBIT 2031 - IPR Page 7
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`

`

`Schubert Declaration
`IPR2017-01608
`
`• Ultra-fast response times;
`
`
`• Ability to generate light output of different colors and dynamic control of
`the different colors;
`
`
`• Digital control with 100% dimming capabilities;
`
`
`• Wider range of operating temperatures including temperatures as cold as
`-40ºC.
`
`
`26. Because of their many advantages over conventional lighting sources,
`
`LEDs are now commonly and increasingly used for a variety of applications,
`
`which vary according to size, shape, light color, light intensity, light dispersion,
`
`and power consumption. Examples of modern-day LED applications include the
`
`following (reproduced from Chang et al., “Light emitting diodes reliability
`
`review,” Microelectronics Reliability 52:762-782 (2012) (Exhibit 2026 at 763)):
`
`
`
`10
`
`EXHIBIT 2031 - IPR Page 8
`
`

`

`Schubert Declaration
`IPR2017-01608
`
`
`
`27. Notwithstanding their many advantages and increasingly widespread
`
`use, the development of LED technology has faced, and still faces a number of
`
`technical and economic challenges. Specifically, the ultimate success of LED-
`
`based products depends strongly on the ability to develop LEDs with even higher
`
`brightness, efficiency, durability, and reliability, while also making these products
`
`ever smaller and cheaper to manufacture.
`
`28. Different design goals, such as the ones recited above, frequently are
`
`in direct tension with each other, and simultaneously achieving all of these
`
`different design goals requires a carefully balanced design that gives consideration
`
`to the various components within the LED. Enhancing one characteristic feature of
`
`an LED may negatively influence another feature. For example, steps taken to
`
`enhance the brightness of an LED may have a negative effect on the device’s
`
`
`
`11
`
`EXHIBIT 2031 - IPR Page 9
`
`

`

`Schubert Declaration
`IPR2017-01608
`
`durability and reliability. This was a challenge at the time of the’250 Patent (about
`
`2008) and remains a challenge in LED device design.
`
`A. LED device technology overview
`
`1. LED device components: structure and function
`
`29. The principal functional component of every LED device is the
`
`semiconductor element, also known as an LED “chip” or “die.”3 When an
`
`electrical current passes through the semiconductor chip, the electrical energy is
`
`converted into light energy.
`
`30. To function properly, the LED chip is housed in an LED “package.”
`
`Various components within the LED package permit several functions, including
`
`(1) supplying an electrical current from an external power source to the LED chip
`
`for light emission; (2) supplying an optical path through which the light emitted
`
`from the LED chip exits the LED package into the surrounding environment; (3)
`
`supplying a thermal path for dissipating the heat generated by the operation of the
`
`LED chip; (4) providing mechanical protection to the LED chip from the external
`
`environment; and (5) providing a mechanical structure through which the LED
`
`(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1) (cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)
`
`3 The term “chip” or “die” is commonly used to refer to the semiconductor element
`that emits light, while the term “package” is commonly used to refer to the
`combination of components to which the semiconductor chip is physically attached
`and electrically connected, as illustrated and discussed below. Although the term
`“device” is sometimes used to refer to the LED chip itself, it is usually used to
`refer to the overall LED device (i.e., the LED chip plus the LED package) (a.k.a.
`packaged LED), and to a final lighting product that includes packaged LEDs.
`
`
`
`12
`
`EXHIBIT 2031 - IPR Page 10
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`

`

`Schubert Declaration
`IPR2017-01608
`
`package is mounted and electrically connected (e.g. by soldering) to an external
`
`mounting substrate.
`
`31. The cross-sectional view of a common packaged LED4 is depicted
`
`below, followed by a brief explanation of each component and its functional role:
`
`
`(adapted from Daniel Lu & C.P. Wong, Materials for Advanced Packaging, p. 646,
`Fig. 18.15 (2009))
`
`
`
`
`32. LED Die: As noted, the LED die is a semiconductor chip that emits
`
`light when an electrical current passes through it. A common semiconductor
`
`material used for LED chips is gallium nitride (GaN). The chip typically has the
`
`(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1) (cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)
`
`4 A “packaged LED” includes the LED chip and the LED package.
`
`
`
`13
`
`EXHIBIT 2031 - IPR Page 11
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`

`

`Schubert Declaration
`IPR2017-01608
`
`size of a grain of salt. The chip includes a rectifying pn junction5 and thus is an
`
`electrical valve or a “diode”.
`
`33. Die Attach Material: The attachment of the LED die to the LED
`
`package is known as “die attach” or “die bonding.” The die attach material is an
`
`adhesive material or paste that is used not only to physically secure the LED chip
`
`within the package, but also to electrically and thermally connect the LED chip
`
`with the surrounding heat-sink area of the LED package, so that electrical power
`
`can be supplied into the chip, and heat can be extracted out of the chip and
`
`package.
`
`34. Leadframe, Leads and Bond Wires: The lead frame may be
`
`considered a “mechanical scaffolding” during the assembly of the packaged LEDs.
`
`The leadframe is a metal frame that includes the ensemble of leads. The leads (or
`
`lead electrodes) supply an electrical current from an external power source outside
`
`the package to the LED chip inside the package. The LED chip is mounted (die-
`
`bonded) to one of the leads and this lead is referred to as the “chip-mounting lead”.
`
`The leads enable the soldering of the packaged LED onto the mounting substrate
`
`such as a printed circuit board (PCB). The leads also can serve as a light reflector
`
`and as a thermal conductor for heat dissipation. The bond wires conduct electricity
`
`(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1) (cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)
`
`5 The letters “p” and “n” in pn junction refer to positive and negative charge
`carriers, respectively.
`
`
`
`14
`
`EXHIBIT 2031 - IPR Page 12
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`

`

`Schubert Declaration
`IPR2017-01608
`
`from the leads to the LED chip. The process of attaching bond wires to the LED
`
`chip at one end, and to the lead electrode at the other end, is known as the “wire
`
`bonding” process.
`
`35. Heat Sink (or Heat Sink Slug): A heat sink (not shown in the figure
`
`above), typically positioned below the mounted LED chip and made of copper or
`
`aluminum, serves to provide a thermal path for dissipating the heat generated
`
`during the operation of the LED chip. This is accomplished by transporting heat
`
`away from the LED chip and releasing it to a mounting substrate, thereby
`
`preventing overheating of the LED chip.
`
`36. Packaging Resin: The packaging resin provides a support structure
`
`connecting the various components of the packaged LED. The packaging resin
`
`frequently has a white color and can reflect and disperse light as controlled by the
`
`material used to form the packaging resin. The material used to form the
`
`packaging resin can be selected from a number of materials, such as, but not
`
`limited to thermoplastic resins6 and thermosetting resins7. The selection of the
`
`packaging material will have significant and wide ranging effects on the packaged
`
`LED, including its mechanical, optical, thermal, chemical, and photochemical
`
`properties as well as its manufacturing process (as described below).
`
`(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1) (cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)
`
`6 Examples of thermoplastic resins are polyphthalamide (PPA) resin and liquid-
`crystal polymer (LCP) resin.
`7 Examples of thermosetting resins are epoxy resin and silicone resin.
`
`
`
`15
`
`EXHIBIT 2031 - IPR Page 13
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`Schubert Declaration
`IPR2017-01608
`37. Encapsulant or Transparent Resin8 (called a “sealing member” in
`
`the ’250 Patent): The encapsulant is a material that is positioned around and on
`
`top of the LED chip so as to encase the LED chip and its attached bond wires. The
`
`encapsulant serves both optical and mechanical purposes. Optically, the
`
`encapsulant is transparent and transmits the light generated by the LED chip,
`
`permitting the emitted light to escape the LED package into the surrounding
`
`environment. The encapsulant may also contain a phosphor that absorbs some of
`
`the light emitted by the LED chip and re-emits the light at a different wavelength
`
`so that the color of the emitted light is modified. The encapsulant can also help
`
`disperse, collimate, or focus the emitted light in a desired direction. The
`
`encapsulant also provides protection to the LED chip and bond wires, by shielding
`
`them from humidity, moisture, and mechanical impact.
`
`38. Mounting Substrate, e.g. PCB9: A mounting substrate, frequently a
`
`printed circuit board (“PCB”) is used to provide an electrical and physical
`
`connection between the LED package and its surrounding environment, so that
`
`electricity can flow through the LED chip and heat can flow away from the LED
`
`chip.
`
`(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1) (cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)
`
`8 The resin is optically transparent or translucent.
`9 PCB = Printed Circuit Board
`
`
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`16
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`B. LED packaging: integrating multiple design challenges
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`39.
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` Effective design of LED packages has become critical to the
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`technological and commercial success of LED lighting products, because the
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`ultimate performance of even the most powerful or sophisticated LED chip will be
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`limited and determined by the overall effectiveness of the accompanying LED
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`package.
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`40. LED package design involves the simultaneous integration and
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`balancing of multiple design goals that pertain to the electrical, optical, thermal,
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`mechanical, chemical and photochemical domains of the LED package. The LED
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`package must accommodate the input electrical power of the LED chip, as well as
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`the output light and heat generated during operation of the LED chip, while
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`maintaining the electrical, optical, thermal, mechanical, chemical, and
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`photochemical properties of the package and its components.
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`1. Electrical design challenges
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`41. The LED package must efficiently and reliably supply electricity to
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`the LED chip to allow for the conversion of electrical energy into optical energy.
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`42. A failure or an interruption in the electrical pathway can occur when
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`the bonding wires break or become detached from their attachment points. Failure
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`also can be caused by the undesirable bleeding or overflow of the electrically
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`conductive adhesive die-attach material within the LED package; this can cause the
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`LED to short circuit.
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`43. Oversupply of electrical current can be detrimental, because increased
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`current generates more thermal, optical, and electrical stress within the LED
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`package.
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`2. Optical design challenges
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`44. The LED package must efficiently and reliably extract the light
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`emitted from the LED chip into the space surrounding the LED package. The light
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`extraction efficiency of the LED package will significantly influence the ultimate
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`energy efficiency10 of the LED lighting product, e.g. an LED light bulb or LED
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`TV, in which the packaged LEDs are installed.
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`45. The light extraction efficiency of the package can be enhanced by a
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`variety of mechanisms, including the selection of appropriate encapsulants that
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`allow light to efficiently pass through the material, as well as the use of reflecting
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`and diffusing materials that enhance light transmission from inside the package to
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`its outside environment.
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`46. An inadequate light extraction efficiency of the package will
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`undermine the energy efficiency and reliability of the LED device, because a
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`(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1) (cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)
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`10 The energy efficiency is defined as the output optical energy divided by the input
`electrical energy of the LED.
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`higher electrical power will be required to generate the desired amount of light,
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`and the increased consumption of electrical energy will in turn generate increased
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`amounts of heat that degrades and damages the various components within the
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`LED package, as I will explain later.
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`3. Mechanical design challenges
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`47. The mechanical design of an LED package also is an important
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`consideration. The LED package must consist of materials that will
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`simultaneously provide mechanical protection to the various components housed
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`within the LED package (such as the LED chip and its attached bond wires),
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`without interfering with the input electrical current and output light and heat.
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`Moreover, because packaged LEDs must be assembled and installed into a
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`downstream product, the shape and structure of the package should be designed to
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`facilitate downstream assembly of individual packaged LEDs into a wide range of
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`final products.
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`4. Thermal design challenges
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`48. Thermal design is important to LED package design because thermal
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`stress resulting from the heat generated by the LED chip will adversely affect LED
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`device performance and lifetime.
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`49. Although LEDs are more energy-efficient than conventional lighting
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`sources, the fact remains that LEDs are not 100% energy efficient, and much but
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`not all of the electrical energy supplied to the LED chip will actually be converted
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`into light energy (usually 40 to 80%), with the remainder lost as heat. Thus, the
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`generation of heat inside the LED package is an unavoidable byproduct that must
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`be addressed and carefully managed during the design phase of the package.
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`Elevated temperatures inside the LED package result in thermal stresses on the
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`LED components that accelerate the aging and adversely impact the LED’s
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`performance and reliability.
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`50. CTE Mismatch. The coefficient of thermal expansion (“CTE”) is a
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`measure that describes the extent to which a material expands and contracts in
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`response to changes in temperature. An LED package typically contains different
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`conducting and insulating materials, each having different coefficients of thermal
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`expansion. In response to the heat generated during LED operation, these different
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`materials will expand and deform at different rates as a result of their different
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`coefficients of thermal expansion.
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`51. LED devices frequently experience recurring cycles of thermal
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`expansion and contraction when the LED is switched ON and OFF. In addition,
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`the packaging materials in LED devices used for outdoor applications may undergo
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`thermal expansion and contraction due to the substantial variations in daily and
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`annual temperature. Over time, the effects of numerous cycles of thermal
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`expansion and contraction can degrade the structural integrity of the LED package
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`and severely degrade LED performance.
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`52. The greater the mismatch (or difference) between the CTEs of the
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`different materials, the greater the thermomechanical stress that will occur as a
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`result of temperature variations. Damage to the LED package as a result of CTE
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`mismatch can occur via at least two common mechanisms.
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`53. First, thermal expansion of the packaging resin material and the
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`encapsulant material creates stress and exerts force on all components of the
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`packaged LED. The heat will be more concentrated in the area surrounding the
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`LED die and, thus, the portion of the packaging resin material and the encapsulant
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`material nearer to the LED die will expand and contract more strongly than the
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`portions of the packaging resin material and the encapsulant material farther from
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`the LED die11, creating stress and thus exerting forces within the reflective and
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`encapsulating resins. This will, in turn, create stress and exert force on the
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`components of the LED, for instance, upon the bonding wires. If the adhesion
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`between a bonding wire and its attachment points (the lead electrode and the LED
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`chip electrode) is sufficiently strong, then the electrical bonding-wire connections
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`will remain intact (and the LED can continue to function). However, if the
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`thermomechanical stress is excessive, the bonding wire can become detached,
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`(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1) (cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)
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`11 I use “nearer” and “farther” in a relative sense. The distances at issue are on the
`order of 1 mm or less.
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`thereby disrupting the supply of current to the LED chip (which will in turn cease
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`to emit light).
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`54.
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`Second, the thermomechanical stress caused by the nonuniform rates
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`of expansion of two materials with different CTEs (coefficients of thermal
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`expansion) can cause delamination, or a mechanical separation at the interface
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`between the two materials. Delamination most often occurs within the recess of
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`the LED package, at the interface between (i) the LED chip and the encapsulating
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`resin, (ii) the encapsulating resin and the lead frame, (iii) the encapsulating resin
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`and the packaging resin, and (iv) at the location where the LED chip is die-bonded
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`to the chip-mounting lead. These locations are indicated by the dashed green lines
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`in the figure below.
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`(adapted from Daniel Lu & C.P. Wong, Materials for Advanced Packaging, p. 646,
`Fig. 18.15 (2009))
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`IPR2017-01608
`55. Delamination can have a number of adverse effects upon the LED
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`package. In general, delamination will result in decreased light output from the
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`LED package, and can also lead to a decrease in heat dissipation from the LED
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`package. If the thermomechanical stresses are sufficiently high, they can also
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`produce physical defects and deformities in the overall shape of the LED package
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`itself, which can adversely affect its functioning.
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`56. Because of the detrimental effects of excessive heat and thermal stress
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`inside the LED pa