Filed on behalf of: Nichia Corporation
`
`
`
`By: Martin M. Zoltick, Lead 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
`Emails: mzoltick@rfem.com
` mjones@rfem.com
` mrawls@rfem.com
`
`
`
`
`
`UNITED STATES PATENT AND TRADEMARK OFFICE
`_______________
`
`BEFORE THE PATENT TRIAL AND APPEAL BOARD
`_______________
`
`LOWE’S COMPANIES, INC.,
`LOWE’S HOME CENTERS, LLC AND L G SOURCING, INC.,
`Petitioner,
`
`v.
`
`NICHIA CORPORATION,
`Patent Owner.
`_______________
`
`Case IPR2017-02014
`Patent 8,530,250
`_______________
`
`DECLARATION OF DR. E. FRED SCHUBERT IN SUPPORT OF
`PATENT OWNER’S PRELIMINARY RESPONSE
`NICHIA EXHIBIT 2001
`Lowe's Cos., Inc. v. Nichia Corp.
`Case IPR2017-02014
`
`

`

`TABLE OF CONTENTS
`
`Schubert Declaration
`IPR2017-02014
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` 
`
`INTRODUCTION ............................................................................................... 1
`I.
`II. QUALIFICATIONS ............................................................................................ 1
`III. MATERIALS CONSIDERED ......................................................................... 7
`IV. SUMMARY OF OPINIONS ............................................................................ 7
`V. TECHNOLOGY BACKGROUND ..................................................................... 8
`A. LED Device Technology Overview ............................................................... 12
`1. LED Device Components: Structure and Function ..................................... 12
`B. LED Packaging: Integrating Multiple Design Challenges ............................ 16
`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 .............................................................. 28
`1. Size .............................................................................................................. 29
`2. Cost .............................................................................................................. 30
`3. High-Throughput Manufacturing Capacity ................................................. 31
`D. Other Differences ........................................................................................... 37
`VI. Definition of One of Ordinary Skill in the Art ............................................... 43
`VII. deficiencies of Grounds presented by Petitioner ............................................ 46
`A. Obviousness .................................................................................................... 46
`B. The Challenged Claims .................................................................................. 53
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`C. Nichia’s ’250 Patent ....................................................................................... 56
`D. The Petition Fails to Establish a Reasonable Likelihood
`That Any One of the Challenged Claims of the ’250 Patent
`Would Be Found Unpatentable ............................................................................ 60
`1. The Petition Fails to Account for
`This Field’s Unpredictability ............................................................................. 61
`2. The Prior Art References Cited in the Petition Have
`Many Important Differences Among Them ...................................................... 63
`3. None of the Grounds Take Into Consideration
`the Differences Between the Prior Art Teachings ............................................. 71
`VIII. CONCLUSION .............................................................................................. 85
` 
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`Schubert Declaration
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`I.
`
`INTRODUCTION
`
`1. My name is E. Fred Schubert, and I have been retained by counsel for
`
`Patent Owner, Nichia Corporation (“Nichia”) to serve as an expert witness in the
`
`above-captioned proceeding based on a Petition for Inter Partes Review (IPR)
`
`filed by Lowe’s Companies, Inc; Lowe’s Home Centers, LLC; and L G Sourcing,
`
`Inc. (the “Lowe’s Petition” or the “Petition”), which challenges certain claims in
`
`Nichia’s U.S. Patent No. 8,530,250 (the “’250 patent”).
`
`2.
`
`I understand that this declaration1 will be submitted in support of the
`
`Patent Owner’s Preliminary Response in the IPR.
`
`3.
`
`The facts and opinions expressed herein are true and accurate to the
`
`best of my knowledge and understanding based on the information I have reviewed
`
`to date.
`
`II. QUALIFICATIONS
`
`4. My curriculum vitae (CV) detailing my educational background and
`
`professional experience is Exhibit A. My CV includes a list of all publications I
`
`have authored, including all publications from the previous ten years.
`
`
`
`1 I submitted a similar declaration in IPR2017-01608 (Paper 8, Ex. 2001), addressing
`substantially similar grounds for a subset of the claims challenged here. My declaration here is
`consistent with my earlier declaration. I have updated it to address the new arguments presented
`in this Petition.
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`5.
`
`I am currently a Full Professor in the Department of Electrical,
`
`Computer, and Systems Engineering at Rensselaer Polytechnic Institute (RPI) in
`
`Troy, New York.
`
`6.
`
`I received a Master’s Degree in Electrical Engineering from the
`
`University of Stuttgart, Germany, in 1981. I received a Ph.D. degree in Electrical
`
`Engineering from the University of Stuttgart, Germany, in 1986. Subsequent to
`
`my education, starting in 1985, I worked in industry at AT&T Bell Laboratories in
`
`Holmdel and Murray Hill, New Jersey, for ten years. In 1995, I joined academia.
`
`My first position was at Boston University (Boston, MA), where I worked as a full
`
`professor for seven years. In 2002, I joined RPI as a distinguished professor, the
`
`Wellfleet Senior Constellation Professor and Head of the Future Chips
`
`Constellation with appointments in the Department for Electrical, Computer, and
`
`Systems Engineering and the Department for Physics, Applied Physics and
`
`Astronomy. I am the founding Director of the Smart Lighting Engineering
`
`Research Center that is funded by the U.S. National Science Foundation at a
`
`volume of $40 million over 10 years.
`
`7.
`
`I am named as co-inventor in more than 30 U.S. patents and have co-
`
`authored more than 300 publications. I authored the books “Doping in III-V
`
`Semiconductors” (1993), “Delta Doping of Semiconductors” (1996), and the first
`
`and second editions of “Light-Emitting Diodes” (2003 and 2006); the latter book is
`
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`known as a standard textbook in the field of LEDs, and the book has been
`
`translated into Russian, Japanese and Korean. My publications have been well
`
`recognized by the technical community as illustrated by the more than 30,000
`
`citations that my publications have received.
`
`8.
`
`I received several awards for my technical contributions. They
`
`include: Senior Member IEEE (1993); Literature Prize of Verein Deutscher
`
`Elektrotechniker for my book “Doping in III-V Semiconductors” (1994); Fellow
`
`SPIE (1999); Alexander von Humboldt Senior Research Award (1999); Fellow
`
`IEEE (1999); Fellow OSA (2000); Boston University Provost Innovation Award
`
`(2000); Discover Magazine Award for Technological Innovation (2000); R&D 100
`
`Award for RCLED (2001); Fellow APS (2001); RPI Trustees Award for Faculty
`
`Achievement (2002 and 2008); honorary membership in Eta Kappa Nu (2004); 25
`
`Most Innovative Micro- and Nano-Products of the Year Award of R&D Magazine
`
`(2007); and Scientific American 50 Award (2007).
`
`9. My general expertise is in the field of electrical engineering and
`
`applied physics including semiconductor materials, processing, and devices. My
`
`specific expertise is in the field of light-emitting diodes (LEDs), including the
`
`structure, packaging, and manufacture of LEDs. My work has included the design,
`
`growth, fabrication, manufacturing, and testing of semiconductor devices as well
`
`as the employment of these devices in a variety of applications.
`
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`10.
`
`I have been working in the field of semiconductor microelectronic and
`
`optoelectronic devices, including light-emitting diodes (LEDs), for more than 30
`
`years. I have conducted and directed research in this field, conducted and directed
`
`development in this field, and have published numerous papers, patents, and books
`
`on the topic of LEDs. My research and development activities have included the
`
`packaging, reliability, life-testing, heat-flow, and encapsulation of LEDs. Specific
`
`packaging-related research topics, which I have personally worked and published
`
`on, include the following:
`
`• The encapsulation of LED chips in an LED package using a transparent
`resin, and the control of the refractive index of the transparent resin by the
`inclusion of TiO2 nanoparticles;
`
`
`
`• The heat flow in LED packages and the thermal management in LED
`packages;
`
`
`
`• The development of new approaches for the over-voltage protection of
`packaged LEDs without the use of Zener diodes;
`
`
`
`• The spatial distribution of phosphor in LED packages including the analysis
`of remote-phosphor distributions;
`
`
`
`• The reliability of LED packages including the lifetime testing under (i)
`elevated temperatures, (ii) enhanced humidity, and (iii) over-current
`conditions; and
`
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`
`
`• Delamination effects of optical thin films under stress conditions occurring
`in optoelectronic packages.
`
`
`
`11.
`
`I have made pioneering contributions to the following technical fields:
`
`Delta-doping, resonant cavity light-emitting diodes, enhanced spontaneous
`
`emission in Er-doped Si/SiO2 microcavities, elimination of unipolar heterojunction
`
`band discontinuities, p-type superlattice doping in AlGaN, photonic-crystal light-
`
`emitting diodes, crystallographic etching of GaN, polarization-enhanced ohmic
`
`contacts, delta-doped ohmic contacts, non-alloyed ohmic contacts, omni-
`
`directional reflectors, low-refractive index materials, anti-reflection coatings, light-
`
`emitting diodes with remote phosphors, the efficiency droop in GaInN LEDs, and
`
`solid-state lighting.
`
`12.
`
`I have extensive experience related to the packaging of LEDs. I have
`
`conducted research and published articles on the following:
`
`• the design, fabrication, and testing of LED packages with particular
`attention to the spatial phosphor distribution;
`
`
`
`• the design and testing of LED packages with particular attention to the
`thermal management of packaged LEDs; and
`
`
`
`• the occurrence of trapped optical modes inside the LED packages.
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`
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`13. Furthermore, I pioneered what is now known as the “remote
`
`phosphor” distribution in white LEDs; the associated research article (entitled
`
`“Strongly enhanced phosphor efficiency in GaInN white light-emitting diodes
`
`using remote phosphor configuration and diffuse reflector cup”) has been cited
`
`more than 300 times.
`
`14.
`
`I have written two editions of a book on LEDs with the second edition
`
`published in 2006; the book contains a chapter dedicated to the packaging of
`
`LEDs.
`
`15. At RPI, I regularly teach a course on LEDs which includes extensive
`
`discussions on the packaging of LEDs. I have guided graduate students and post-
`
`doctoral researchers conducting research on the packaging of LEDs. My work in
`
`industry (AT&T Bell Laboratories) included the packaging of LEDs and lasers,
`
`including minimizing the cost of device packaging processes.
`
`16.
`
`I am the founding director of the Smart Lighting Engineering
`
`Research Center funded by the US National Science Foundation; this center
`
`concerns LEDs and the packaging of these devices to make intelligent or “smart”
`
`lighting systems.
`
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`17.
`
`I consider myself to have at least the same level of skill and
`
`experience as the person of ordinary skill in the art (POSITA) to which the ’250
`
`patent is directed, and had so as of the time of the invention (approximately 2008).
`
`III. MATERIALS CONSIDERED
`
`18.
`
`In preparation of this declaration and the opinions set forth herein, I
`
`have considered the Petition filed by Lowe’s and the supporting exhibits, including
`
`Dr. Shanfield’s declaration, and the references relied on by the Petition and Dr.
`
`Shanfield. In addition, I have also considered the documents, data, and other
`
`information mentioned and cited to herein and in the Exhibits accompanying
`
`Nichia’s Preliminary Response. My opinions are also based upon my knowledge,
`
`education, experience, research, and training in this field that I have accumulated
`
`over the course of my career.
`
`IV. SUMMARY OF OPINIONS
`
`19.
`
`It is my opinion that claims 1-2, 7, 11-12, 15-17, 19, and 21 of U.S.
`
`Patent No. 8,530,250 (“’250 patent”) are not rendered obvious by the references
`
`cited in Lowe’s petition. Furthermore, in studying the petition and accompanying
`
`expert declaration submitted by Dr. Shanfield, it is my opinion that the petition and
`
`declaration fail to even make a reasonable argument that any one of claims 1-2, 7,
`
`11-12, 15-17, 19, and 21 of the ’250 patent is rendered obvious by the references.
`
`As explained below, this is at least because the petition and declaration fail to
`
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`Schubert Declaration
`IPR2017-02014
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`account for key design considerations that one of ordinary skill in the art would
`
`have needed to consider at the time of the invention.
`
`V. TECHNOLOGY BACKGROUND
`
`20. 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.
`
`21. 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
`
`lifespans on the order of 25,000 hours or longer. By comparison, a typical
`
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`Schubert Declaration
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`incandescent light bulb lasts only approximately 1,000 hours before completely
`
`burning out.
`
`22. 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 BTUs2—
`
`nearly equal to the total annual energy consumed by 45 million U.S. homes.3
`
`23. LEDs are environmentally friendly, more so than conventional light
`
`sources. LEDs 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.
`
`24. 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;
`
`
`
`• Ultra-fast response times;
`
`
`
`2 British Thermal Unit (BTU) is an energy unit. 1 kWh is equal to 3412.14 BTUs
`3 See http://energy.gov/eere/ssl/why-ssl.
`
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`• Ability to generate light output of different colors and dynamic control of
`the different colors;
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`Schubert Declaration
`IPR2017-02014
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`
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`• Digital control with 100% dimming capabilities;
`
`
`
`• Wider range of operating temperatures including temperatures as cold as
`-40ºC
`
`
`
`25. 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) (Ex. 2025 at 763)):
`
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`Schubert Declaration
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`
`
`26. 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.
`
`27. 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
`
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`Schubert Declaration
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`enhance the brightness of an LED may have a negative effect on the device’s
`
`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
`
`28. The principal functional component of every LED device is the
`
`semiconductor element, also known as an LED “chip” or “die.”4 When an
`
`electrical current passes through the semiconductor chip, the electrical energy is
`
`converted into light energy.
`
`29. 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
`
`
`
`4 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.
`
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`package is mounted and electrically connected (e.g. by soldering) to an external
`
`mounting substrate.
`
`30. The cross-sectional view of a common packaged LED5 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))
`
`
`
`
`31. 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
`
`size of a grain of salt. The chip includes a rectifying pn junction6 and thus is an
`
`electrical valve or a “diode”.
`
`
`
`5 A “packaged LED” includes the LED chip and the LED package.
`6 The letters “p” and “n” in pn junction refer to positive and negative charge carriers,
`respectively.
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`32. 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.
`
`33. 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
`
`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 “wire
`
`bonding” process.
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`34. 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.
`
`35. 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 resins7 and thermosetting resins8. 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).
`
`36. Encapsulant or Transparent Resin9: The encapsulant is a material
`
`that is positioned around and on top of the LED chip so as to encase the LED chip
`
`
`
`7 Examples of thermoplastic resins are polyphthalamide (PPA) resin and liquid-crystal polymer
`(LCP) resin.
`8 Examples of thermosetting resins are epoxy resin and silicone resin.
`9 The resin is optically transparent or translucent.
`
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`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.
`
`37. Mounting Substrate, e.g. PCB10: 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.
`
`B. LED Packaging: Integrating Multiple Design Challenges
`
`38. Effective design of LED packages has become critical to the
`
`technological and commercial success of LED lighting products, because the
`
`ultimate performance of even the most powerful or sophisticated LED chip will be
`
`
`
`10 PCB = Printed Circuit Board
`
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`limited and determined by the overall effectiveness of the accompanying LED
`
`package.
`
`39. LED package design involves the simultaneous integration and
`
`balancing of multiple design goals that pertain to the electrical, optical, thermal,
`
`mechanical, chemical and photochemical domains of the LED package. The LED
`
`package must accommodate the input electrical power of the LED chip, as well as
`
`the output light and heat generated during operation of the LED chip, while
`
`maintaining the electrical, optical, thermal, mechanical, chemical, and
`
`photochemical properties of the package and its components.
`
`1. Electrical Design Challenges
`
`40. The LED package must efficiently and reliably supply electricity to
`
`the LED chip to allow for the conversion of electrical energy into optical energy.
`
`41. A failure or an interruption in the electrical pathway can occur when
`
`the bonding wires break or become detached from their attachment points. Failure
`
`also can also be caused by the undesirable bleeding or overflow of the electrically
`
`conductive adhesive die-attach material within the LED package; this can cause the
`
`LED to short circuit.
`
`42. Oversupply of electrical current can be detrimental, because increased
`
`current generates more thermal, optical, and electrical stress within the LED
`
`package.
`
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`Schubert Declaration
`IPR2017-02014
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`2. Optical Design Challenges
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`43. 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 efficiency11 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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`44. 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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`45. 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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`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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`
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`11 The energy efficiency is defined as the output optical energy divided by the input electrical
`energy of the LED.
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`Schubert Declaration
`IPR2017-02014
`
`3. Mechanical Design Challenges
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`46. 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 wide range of
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`final products.
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`4. Thermal Design Challenges
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`47. 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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`48. 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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`Schubert Declaration
`IPR2017-02014
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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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`49. 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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`50. 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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`51. 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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`Schubert Declaration
`IPR2017-02014
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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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`52. First, thermal expansion of the packaging resin material and the
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`encapsulant material creates stress and exert 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 m