Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L2/00—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor
  • A61L2/02—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor using physical phenomena
  • A61L2/08—Radiation
  • A61L2/10—Ultraviolet radiation
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  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
  • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
  • H10H20/80—Constructional details
  • H10H20/84—Coatings, e.g. passivation layers or antireflective coatings
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  • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
  • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
  • H10H20/80—Constructional details
  • H10H20/85—Packages
  • H10H20/8506—Containers
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
  • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
  • H10H20/80—Constructional details
  • H10H20/85—Packages
  • H10H20/852—Encapsulations
  • H10H20/853—Encapsulations characterised by their shape
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
  • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
  • H10H20/80—Constructional details
  • H10H20/85—Packages
  • H10H20/852—Encapsulations
  • H10H20/854—Encapsulations characterised by their material, e.g. epoxy or silicone resins
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
  • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
  • H10H20/80—Constructional details
  • H10H20/85—Packages
  • H10H20/855—Optical field-shaping means, e.g. lenses
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
  • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
  • H10H20/80—Constructional details
  • H10H20/85—Packages
  • H10H20/855—Optical field-shaping means, e.g. lenses
  • H10H20/856—Reflecting means
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
  • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
  • H10H20/80—Constructional details
  • H10H20/85—Packages
  • H10H20/857—Interconnections, e.g. lead-frames, bond wires or solder balls
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
  • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
  • H01L2224/10—Bump connectors; Manufacturing methods related thereto
  • H01L2224/15—Structure, shape, material or disposition of the bump connectors after the connecting process
  • H01L2224/16—Structure, shape, material or disposition of the bump connectors after the connecting process of an individual bump connector
  • H01L2224/161—Disposition
  • H01L2224/16135—Disposition the bump connector connecting between different semiconductor or solid-state bodies, i.e. chip-to-chip
  • H01L2224/16145—Disposition the bump connector connecting between different semiconductor or solid-state bodies, i.e. chip-to-chip the bodies being stacked
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
  • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
  • H01L2224/42—Wire connectors; Manufacturing methods related thereto
  • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
  • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
  • H01L2224/4805—Shape
  • H01L2224/4809—Loop shape
  • H01L2224/48091—Arched
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/15—Details of package parts other than the semiconductor or other solid state devices to be connected
  • H01L2924/181—Encapsulation
  • H01L2924/1815—Shape
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
  • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
  • H10H20/01—Manufacture or treatment
  • H10H20/036—Manufacture or treatment of packages
  • H10H20/0362—Manufacture or treatment of packages of encapsulations
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
  • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
  • H10H20/01—Manufacture or treatment
  • H10H20/036—Manufacture or treatment of packages
  • H10H20/0363—Manufacture or treatment of packages of optical field-shaping means
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
  • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
  • H10H20/01—Manufacture or treatment
  • H10H20/036—Manufacture or treatment of packages
  • H10H20/0364—Manufacture or treatment of packages of interconnections

Definitions

• the present invention relates to light emitters emitting ultraviolet (UV) radiation.
• UV ultraviolet
• FIG. 1 depicts a conventional LED package 100, in which an LED chip 105 is electrically and physically connected to a submount 110 on a surface-mount device (SMD) package 115. Wires 120 electrically connect submount contacts to contact pads 125 on the SMD package 115, and a plastic lens 130 is placed over the LED chip 105 to focus the light therefrom.
• SMD surface-mount device
• a transparent liquid- or gel-based "glob top" encapsulant 135 is then disposed over all of the components within the SMD package 115 and cured to form a semi-rigid protective coating that is also transparent to light emitted by the LED chip 105.
• the encapsulant 135 typically has a lens-like shape to facilitate light emission from the packaged LED chip 105.
• LED package 100 also may feature one or more electrical contacts 140 that electrically connect the LED chip 105 to the submount 110, as well as an underfill 145. As shown, the underfill 145 may be disposed between the LED chip 105 and the submount 110 and provide mechanical support to the LED chip between the electrical contacts 140.
• UV LEDs have shown great promise for applications such as medical therapy, sensors and instrumentation, and fluid sterilization.
• the above-described conventional packaging is frequently unsuitable for UV LEDs, which may emit light having wavelengths less than 320 nm, less than 265 nm, or even less than 200 nm.
• the highly energetic UV light leads to deterioration and even formation of cracks 150 within the transparent encapsulant. Such cracking may lead to distortions or breaks in the bonding wires 120 or failure of the LED package 100 due to moisture introduced from the outside environment along the cracks 150.
• UV radiation from UV LEDs can cause deterioration and even failure of the plastic lenses 130 that are typically utilized atop other (e.g., visible- light-emitting) LEDs.
• other LEDs e.g., visible- light-emitting
• high- reliability packages for UV LED chips include rigid lenses resistant to UV damage or deterioration in combination with a barrier layer between light-emitting portions of the LED chip and any transparent encapsulant utilized to encase the LED chip within the package.
• the barrier layer substantially prevents transmission of UV light through the majority of such encapsulant, thereby preventing deterioration and cracking (or other mechanical failure) thereof.
• the barrier layer includes or consists essentially of a portion of the encapsulant itself that is adjacent to the LED chip and opaque to the UV light emitted by the LED chip.
• the remaining portion of the encapsulant farther away from the LED chip may also be UV-opaque or transparent, as this more distant encapsulant will typically not transmit the emitted UV light.
• an "opaque" material substantially does not transmit light of a particular wavelength or wavelength range (e.g., UV light), and instead is reflective and/or strongly absorptive (e.g., over a small thickness) to light of the particular wavelength or wavelength range.
• the barrier layer includes or consists essentially of a solid opaque shield disposed between the LED chip and the encapsulant, which may itself therefore be transparent or opaque to UV light.
• the shield may be composed of a metal that is substantially reflective to UV light such as aluminum. In this manner, embodiments of the invention include packaged UV LEDs having long lifetimes, high output power, and high reliability.
• a force is applied between the LED chip and a lens (e.g., a rigid lens) thereover in order to maintain contact therebetween during thermal curing of the encapsulant material and/or during UV emission (e.g., during operation and/or during burn-in processes in manufacturing).
• the force may be a downward force applied to the lens toward the LED chip, an upward force applied to the LED chip toward the lens, or a combination of both.
• the force may advantageously suppress or substantially prevent formation of bubbles within and/or at a thin layer of an interface material that is disposed between the LED chip and the lens.
• Such bubbles may be due, at least in part, to, e.g., gas generated by decomposition of the interface material during curing and/or during UV emission while the LED is in operation.
• gas generated by decomposition of the interface material during curing and/or during UV emission while the LED is in operation.
• application of heat to an interface material including or consisting essentially of silicone may result in the formation of bubbles of formaldehyde gas.
• the emitted UV light may induce a photochemical reaction that takes place in the interface material, and this reaction may result in decomposition of silicone that may result in the formation of bubbles within the interface material.
• the presence of the bubbles may deleteriously impact the UV transparency of the interface material, and, if large enough, may result in at least partial detachment of the lens from the LED chip.
• the force which may have a magnitude of, e.g., between approximately 0.05 Newtons and approximately 10 Newtons, may be applied by a portion of the encapsulant itself that vertically overlaps the lens.
• the encapsulant may thermally contract (due to, e.g., heat-induced volumetric shrinkage) and thereby apply the bubble-preventing force to the lens.
• the encapsulant may include, consist essentially of, or consist of a "heat- contractive material," i.e., a material that experiences volumetric contraction upon application of heat.
• the volumetric contraction typically remains, at least in part, after heating is complete (i.e., the original volume of the heat-contractile material is not recovered, at least not entirely, after the heating is finished).
• the heat-contractive material may include, consist essentially of, or consist of, for example, a resin, e.g., a resin of polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK), a fluoropolymer such as a perfluoroalkoxy alkane (PFA), and/or epoxy.
• epoxy resin may be utilized for its advantageous moisture-blocking properties.
• heat-contractive materials in accordance with embodiments of the present invention are elastic, and retain at least a portion of their elasticity after volumetric contraction, at least a portion of the force applied thereby during curing is retained even after curing (and in the absence of applied heat).
• the force may continue to be applied by the heat-contractive material for a period of at least 10,000 hours, or even at least 50,000 hours, and/or for a time period substantially equal to or exceeding the expected lifetime of one or more other components (e.g., the LED chip) of packaged UV LEDs in accordance with embodiments of the present invention.
• embodiments of the invention feature an illumination device that includes or consists essentially of a light-emitting device, a package, an encapsulant, and a barrier layer.
• the light-emitting device is configured to emit ultraviolet (UV) light and may have at least two spaced-apart contacts. At least a portion of the package may be disposed beneath the light-emitting device. The contacts of the light-emitting device are electrically connected to the package.
• the light-emitting device may be mechanically attached to a portion of the package.
• the encapsulant may be disposed on the package. The encapsulant at least partially surrounds the light-emitting device.
• the barrier layer is disposed between the light-emitting device and the encapsulant.
• the barrier layer is configured (e.g., sized and/or shaped and/or positioned) to substantially prevent UV light emitted by the light-emitting device from entering the encapsulant.
• Embodiments of the invention may include one or more of the following in any of a variety of combinations.
• the barrier layer may include, consist essentially of, or consist of a second encapsulant disposed adjacent to the light-emitting device.
• the second encapsulant may be opaque to UV light emitted by the light-emitting device.
• the encapsulant may be substantially transparent to UV light emitted by the light-emitting device.
• the encapsulant may be opaque to UV light emitted by the light-emitting device.
• the encapsulant and the second encapsulant may include, consist essentially of, or consist of the same material.
• a penetration length of UV light (e.g., the UV light emitted by the light-emitting device and/or UV light having a wavelength range partially or fully overlapping with that of the UV light emitted by the light-emitting device) within the second encapsulant may be less than 25 ⁇ , or even less than 10 ⁇ .
• a penetration length of UV light within the encapsulant may be 100 ⁇ or more (and may even be longer than a dimension, e.g., width, radius, etc., of the encapsulant).
• the barrier layer may include, consist essentially of, or consist of a material reflective to UV light emitted by the light-emitting device.
• the barrier layer may include, consist essentially of, or consist of aluminum.
• At least a portion of the encapsulant may be substantially transparent to UV light emitted by the light-emitting device.
• At least a portion of the encapsulant may be substantially opaque to UV light emitted by the light-emitting device.
• the UV light emitted by the light-emitting device may have a wavelength of 265 nm or less, or even 200 nm or less (and may have a wavelength of 10 nm or more).
• the package may include or consist essentially of a submount and a surface-mount-device (SMD) package.
• SMD surface-mount-device
• the contacts of the light- emitting device may be electrically and mechanically connected to the submount.
• the submount may be disposed above the SMD package and/or may be electrically connected to the SMD package.
• the submount may be electrically connected to the SMD package via one or more wire bonds.
• a rigid inorganic lens may be disposed above the light-emitting device and may at least partially protrude from the encapsulant.
• the lens may include, consist essentially of, or consist of quartz, fused silica, and/or sapphire.
• a top surface of the encapsulant (e.g., the top surface of the encapsulant adjoining and/or in contact with the lens) may be disposed above a bottom surface of the lens by at least 0.05 mm.
• At least a portion of the encapsulant may apply a downward force on the lens toward the light- emitting device.
• the magnitude of the downward force may be greater than 0.1 N.
• a thin interface material e.g., a gel, resin, cured or at least partially uncured polymer, or liquid
• the interface material may have a thickness less than 5 ⁇ .
• the interface material may include, consist essentially of, or consist of silicone (e.g., a silicon resin).
• At least a portion of the encapsulant may apply a downward force on the lens and/or on the interface material toward the light-emitting device.
• the magnitude of the downward force may be greater than 0.1 N.
• the light-emitting device may include, consist essentially of, or consist of a light-emitting diode (e.g., a bare-die light-emitting diode or light-emitting diode chip) or a laser (e.g., a bare-die laser or laser chip).
• the encapsulant may include, consist essentially of, or consist of a heat-contractive material.
• the encapsulant may include, consist essentially of, or consist of polytetrafluoroethylene, polyetheretherketone, a fluoropolymer such as a perfluoroalkoxy alkane, and/or epoxy (e.g., a resin of one or more of these materials).
• the encapsulant may include, consist essentially of, or consist of epoxy (e.g., epoxy resin).
• inventions of the invention feature a method for forming an illumination device.
• An apparatus includes, consists essentially of, or consists of a light-emitting device configured to emit ultraviolet (UV) light, a rigid inorganic lens disposed over the light-emitting device, an interface material disposed between the light-emitting device and the lens, and an encapsulant.
• the encapsulant at least partially surrounds the light-emitting device and contacts at least a portion of the lens.
• the lens may at least partially protrude from the encapsulant.
• the encapsulant is partially or substantially fully cured.
• a downward force is applied on the lens toward the light-emitting device (equivalently, the light-emitting device may be forced upward toward the lens and/or the light-emitting device and lens may be forced toward each other).
• the downward force (i) substantially prevents partial or full detachment of the lens from the light-emitting device, and/or (ii) substantially suppresses formation of bubbles between the light-emitting device and the lens (and/or substantially prevents bubbles from remaining between the light-emitting device and the lens).
• Embodiments of the invention may include one or more of the following in any of a variety of combinations.
• the apparatus may include a barrier layer configured to substantially prevent UV light emitted by the light-emitting device from entering the encapsulant.
• the barrier layer may be disposed between the light-emitting device and the encapsulant.
• the barrier layer may include, consist essentially of, or consist of a second encapsulant disposed adjacent to the light-emitting device (and may be in contact with the light-emitting device).
• the second encapsulant may be opaque to UV light emitted by the light-emitting device.
• the encapsulant may be substantially transparent to UV light emitted by the light-emitting device.
• the encapsulant may be opaque to UV light emitted by the light-emitting device.
• the encapsulant and the second encapsulant may include, consist essentially of, or consist of the same material.
• a penetration length of UV light within the second encapsulant is less than or equal to 25 ⁇ , or even less than or equal to 10 ⁇ .
• a penetration length of UV light within the encapsulant may be 100 ⁇ or more.
• the barrier layer may include, consist essentially of, or consist of a material reflective to UV light emitted by the light-emitting device.
• the barrier layer may include, consist essentially of, or consist of aluminum.
• At least a portion of the encapsulant may be substantially transparent to UV light emitted by the light-emitting device.
• At least a portion of the encapsulant may be opaque to UV light emitted by the light-emitting device.
• the UV light emitted by the light-emitting device may have a wavelength of 265 nm or less, or even 200 nm or less.
• the lens may include, consist essentially of, or consist of quartz, fused silica, and/or sapphire.
• a top surface of the encapsulant may be disposed above a bottom surface of the lens by at least 0.05 mm.
• the magnitude of the downward force may be greater than 0.1 N.
• the downward force may be applied by contraction of at least a portion of the encapsulant during partial curing or substantially full curing of the encapsulant.
• the interface material may have a thickness less than 5 ⁇ .
• the interface material may include, consist essentially of, or consist of silicone (e.g., silicone resin).
• the light-emitting device may include, consist essentially of, or consist of a light-emitting diode (e.g., a bare-die light-emitting diode or light-emitting diode chip) or a laser (e.g., a bare-die laser or laser chip).
• the encapsulant may include, consist essentially of, or consist of a heat-contractive material.
• the encapsulant may include, consist essentially of, or consist of polytetrafluoroethylene, polyetheretherketone, a fluoropolymer such as a perfluoroalkoxy alkane, and/or epoxy (e.g., a resin of one or more of these materials).
• the encapsulant may include, consist essentially of, or consist of epoxy (e.g., epoxy resin).
• the downward force may substantially suppress formation of bubbles arising from decomposition of the interface material (and/or substantially prevent such bubbles from remaining between the light- emitting device and the lens).
• embodiments of the invention feature a method for emitting ultraviolet (UV) light using a light-emitting device at least partially surrounded by an encapsulant.
• Power is supplied to the light-emitting device, thereby causing the light- emitting device to emit UV light.
• UV light emitted by the light- emitting device is substantially prevented from entering (and/or deteriorating, and/or cracking, and/or penetrating more than 25 ⁇ into, or even penetrating more than 10 ⁇ into) the encapsulant.
• Embodiments of the invention may include one or more of the following in any of a variety of combinations.
• the penetration length of UV light within the encapsulant may be 100 ⁇ or more.
• UV light emitted by the light-emitting device may be prevented from entering the encapsulant at least in part by a barrier layer disposed between the light-emitting device and the encapsulant.
• the barrier layer may include, consist essentially of, or consist of a second encapsulant disposed adjacent to the light-emitting device.
• the second encapsulant may be opaque to UV light emitted by the light-emitting device.
• the encapsulant may be substantially transparent to UV light emitted by the light-emitting device.
• the encapsulant may be substantially opaque to UV light emitted by the light-emitting device.
• the encapsulant and the second encapsulant may include, consist essentially of, or consist of the same material.
• a penetration length of UV light within the second encapsulant is less than or equal to 25 ⁇ , or even less than or equal to 10 ⁇ .
• the barrier layer may include, consist essentially of, or consist of a material reflective to UV light emitted by the light-emitting device.
• the barrier layer may include, consist essentially of, or consist of aluminum. At least a portion of the encapsulant may be substantially transparent to UV light emitted by the light-emitting device.
• At least a portion of the encapsulant may be opaque to UV light emitted by the light-emitting device.
• the UV light emitted by the light-emitting device may have a wavelength of 265 nm or less, or even 200 nm or less.
• a rigid inorganic lens may be disposed above the light-emitting device and at least partially protrude from the encapsulant.
• the lens may include, consist essentially of, or consist of quartz, fused silica, and/or sapphire.
• a top surface of the encapsulant may be disposed above a bottom surface of the lens by at least 0.05 mm.
• a force e.g., a downward force
• the magnitude of the force may be greater than 0.1 N.
• An interface material may be disposed between the lens and the light- emitting device.
• the interface material may have a thickness less than 5 ⁇ .
• the interface material may include, consist essentially of, or consist of silicone. At least a portion of the encapsulant may apply a downward force on the lens toward the light- emitting device.
• the magnitude of the downward force may be greater than 0.1 N.
• the light-emitting device may include, consist essentially of, or consist of a light-emitting diode (e.g., a bare-die light-emitting diode or light-emitting diode chip) or a laser (e.g., a bare-die laser or laser chip).
• the encapsulant may include, consist essentially of, or consist of a heat-contractive material.
• the encapsulant may include, consist essentially of, or consist of polytetrafluoroethylene, polyetheretherketone, a fluoropolymer such as a perfluoroalkoxy alkane, and/or epoxy (e.g., a resin of one or more of these materials).
• the encapsulant may include, consist essentially of, or consist of epoxy (e.g., epoxy resin).
• Figure 1 is a cross- sectional schematic of a conventional packaged LED
• Figure 2 is a cross- sectional schematic of a packaged UV LED in accordance with various embodiments of the invention.
• Figure 3 is a cross- sectional schematic of a packaged UV LED in accordance with various embodiments of the invention.
• Figure 4 is a plan-view photograph of a packaged UV LED lacking a UV- blocking barrier between the UV LED chip and a transparent encapsulant after reliability testing; and Figure 5 is a plan-view photograph of a packaged UV LED incorporating a UV-blocking barrier layer in accordance with various embodiments of the invention after reliability testing.
• FIG. 2 is a cross- sectional view of a packaged UV LED 200 in accordance with various embodiments of the present invention.
• a UV LED chip 205 is electrically and mechanically connected to the submount 110, which is itself electrically connected via one or more wire bonds 120 to the SMD package 115.
• the submount 110 may include or consist essentially of, e.g., a ceramic material, and may have electrically conductive pads thereon to which wires 120 and electrical contacts 140 are electrically connected.
• the submount 110 may be thermally conductive in order to conduct heat away from UV LED chip 205 during operation.
• submount 110 may include or consist essentially of aluminum nitride and/or aluminum oxide.
• the submount 110 may include or consist essentially of one or more metals, e.g., copper, or one or more semiconductor materials, e.g., silicon.
• one or more of the inner surfaces (i.e., the surfaces facing the UV LED chip 205) of the SMD package 115 are reflective to the UV light emitted by UV LED chip 205.
• the SMD package 115 may include, consist essentially of, or consist of, for example, one or more plastics such as polyphthalamide (PPA) and/or one or more ceramics such as aluminum nitride or alumina.
• one or more surfaces (or even the entirety) of the SMD package 115 may be coated with a material reflective to UV light (e.g., aluminum).
• the inner surface of SMD package 115 i.e., the surface facing the UV LED chip 205, may be coated with aluminum formed by, e.g., non-electrolytic plating.
• the UV LED chip 205 may include an A1N substrate and, thereover, one or more quantum wells and/or strained layers including or consisting essentially of A1N, GaN, InN, or any binary or tertiary alloy thereof.
• UV LED 205 includes a substrate and/or device structure resembling those detailed in U.S. Patent No. 7,638,346, filed on August 14, 2006, U.S. Patent No. 8,080,833, filed on April 21, 2010, and/or U.S. Patent Application Publication No. 2014/0264263, filed on March 13, 2014, the entire disclosure of each of which is incorporated by reference herein.
• an inorganic (and typically rigid) lens 210 e.g., a lens including or consisting essentially of fused silica, quartz, and/or sapphire
• an interface material 215 e.g., an organic, UV-resistant encapsulant compound that may include or consist essentially of a silicone resin
• An exemplary interface material 215 that may be utilized in embodiments of the present invention is Deep UV-200 available from Schott North America, Inc. of Elmsford, NY.
• an "interface material” is a material that substantially fills any air gaps between, for example, a light-emitting device and a lens.
• the interface material has an index of refraction substantially matched to at least one of the components joined thereby, or an index of refraction that lies between those of the components joined by the interface material.
• Interface materials may be liquid or gelatinous when applied, but may be curable to form substantially solid layers. Interface materials may or may not be intrinsically adhesive.
• the thin layer of interface material 215 is preferably quite thin (e.g., less than 5 ⁇ thick, or even 3 ⁇ thick or less) to minimize or prevent deterioration thereof by the energetic UV radiation from the UV LED chip 205.
• the thickness of the interface material 215 may be at least 1 ⁇ .
• the inorganic lens 210 is itself resistant to UV-light- induced deterioration.
• an encapsulant 220 encases the UV LED chip 205 within the SMD package 115; as shown, the encapsulant 220 may not entirely cover (and may not even contact) the rigid inorganic lens 210. At least a portion of the encapsulant 220 (e.g., the portion of the encapsulant 220 bordering and/or in contact with the UV LED chip 205 and/or the lens 210) may be substantially opaque to the UV light emitted by the UV LED chip 205; thus, any UV light emitted into the encapsulant 220 is confined in an extremely shallow depth of the encapsulant 220, and the energetic UV light does not interact with most of the encapsulant 220. Thus, the encapsulant 220 is more resistant to deterioration and cracking, and the packaged UV LED 200 exhibits greater reliability.
• the penetration length of UV light (e.g., light having a wavelength of 265 nm or less, or even 200 nm or less) of the encapsulant 220 i.e., the distance within the encapsulant 220 during which the intensity of the light decreases to 10% or less of the incident value, is less than 25 ⁇ , or even less than 10 ⁇ .
• conventional encapsulants having penetration lengths of UV light of more than 100 ⁇ may exhibit deterioration and mechanical breakdown after being subjected to UV light.
• the encapsulant 220 includes or consists essentially of black epoxy resin (i.e., epoxy resin having therewithin one or more pigments to give the resin a black color).
• the encapsulant 220 may include a plurality of beads (e.g., glass beads) and/or other fillers therewithin.
• a shallow portion (or "barrier layer") 225 of the encapsulant 220 immediately surrounding the UV LED chip 205 may be a barrier to UV light, and a remaining portion 230 of the encapsulant 220 farther from the UV LED chip 205 may even be transparent and/or non-UV-resistant, as it will not be subjected to the energetic radiation from the UV LED chip 205.
• all of the encapsulant 220 is UV opaque, while in other embodiments of the invention the remaining portion 230 of the encapsulant 220 is substantially UV transparent.
• the UV- opaque barrier layer 225 may be dispensed and/or molded around the UV LED chip 205 before the remaining encapsulant 220 (i.e., portion 230) is disposed around the barrier layer 225 and the UV LED chip 205.
• substantially all of the light emitted from the packaged UV LED 200 is emitted through the rigid lens 210 at the top of the package.
• the barrier layer 225 and the portion 230 of the encapsulant may include, consist essentially of, or consist of different materials, or barrier layer 225 and portion 230 may be composed of one or more of the same materials (such as epoxy, e.g., epoxy resin), with the barrier layer 225 including one or more other components (e.g., pigment) making barrier layer 225 substantially UV opaque.
• materials such as epoxy, e.g., epoxy resin
• barrier layer 225 including one or more other components (e.g., pigment) making barrier layer 225 substantially UV opaque.
• the encapsulant 220 (e.g., barrier layer 225) vertically overlaps the lens 210 as shown in Figure 2.
• the top surface of the encapsulant 220 (at least the portion of the encapsulant immediately proximate and/or in contact with lens 210) is higher than the bottom surface of lens 210 by a distance of at least 0.02 mm, at least 0.05 mm, or even at least 0.1 mm.
• This vertical overlap of the encapsulant 220 may advantageously suppress or substantially prevent formation of bubbles within the interface material 215 (or between the interface material 215 and the lens 210 and/or the UV LED chip 205) and/or suppress or substantially prevent partial or full detachment of the lens 210 (and/or at least a portion of the interface material 215) from the UV LED chip 205 during thermal curing of the encapsulant 220 and/or during UV emission (e.g., during operation and/or during burn-in processes in manufacturing).
• the encapsulant 220 when the encapsulant 220 is cured by e.g., application of heat, at least a portion of the encapsulant 220 may thermally contract (due to, e.g., heat- induced volumetric shrinkage of the encapsulant 220) and thereby apply a downward force (or "down force") on lens 210.
• the encapsulant 220 may thus include, consist essentially of, or consist of a heat-contractive material, e.g., a resin of polytetrafhioroethylene, polyetheretherketone, a fhioropolymer such as a perfluoroalkoxy alkane, and/or epoxy.
• the amount of downward force imposed on lens 210 may be, e.g., more than 0.05 Newtons (N), more than 0.1 N, or even more than 0.2 N.
• the amount of downward force may be less than or equal to 10 N.
• the downward force may advantageously force the lens 210 toward the UV LED chip 205, maintaining contact therebetween, and thereby suppress or substantially prevent formation of bubbles at interface material 215.
• bubbles may be due, at least in part, to, e.g., gas generated by decomposition of the interface material 215 during curing and/or during UV emission while the packaged UV LED 200 is in operation.
• application of heat to an interface material 215 including or consisting essentially of silicone may result in the formation of bubbles of formaldehyde gas.
• the emitted UV light may induce a photochemical reaction that takes place in the interface material 215, and this reaction may result in decomposition of silicone that may result in the formation of bubbles within the interface material 215.
• the presence of the bubbles may deleteriously impact the UV transparency of the interface material 215, and, if large enough, may result in at least partial detachment of lens 210 from the UV LED chip 205.
• the barrier layer 225 of encapsulant 220 may be augmented or replaced with a non-encapsulant barrier 305 that is substantially opaque to the UV light emitted by the UV LED chip 205.
• the non-encapsulant barrier 305 may include, consist essentially of, or consist of a UV- reflective metal layer (e.g., aluminum and/or polytetrafluoroethylene (PTFE) or a derivative thereof) disposed around portions of the UV LED chip 205 that would otherwise contact and/or emit light into the surrounding encapsulant 220.
• a UV- reflective metal layer e.g., aluminum and/or polytetrafluoroethylene (PTFE) or a derivative thereof
• the non- encapsulant barrier 305 may be deposited, molded, or otherwise disposed around portions of the UV LED chip 205 that would otherwise contact and/or emit light into the encapsulant 220 and prevents UV light from entering and deteriorating the surrounding encapsulant 220.
• the non-encapsulant barrier 305 may be a layer or foil deposited or wrapped around the UV LED chip 205 prior to packaging.
• the non-encapsulant barrier 305 may be attached to one or more portions the package (e.g., the SMD package and/or submount) prior to the UV LED chip 205 being disposed within and electrically and/or mechanically connected to one or more portions of the package.
• FIG 3 depicts the barrier layer 225 of the encapsulant 220 present between the non-encapsulant barrier 305 and the remaining portion 230 of the encapsulant 220, in various embodiments of the invention the barrier layer 225 may be omitted (and thus, substantially all of the encapsulant 220 present in packaged UV LED 300 may be substantially UV transparent). In other embodiments, all or a portion of the barrier layer 225 may be disposed between the UV LED chip 205 and the non-encapsulant barrier 305.
• Reliability testing was performed on 15 packaged UV LEDs, six control devices utilizing transparent encapsulant without a barrier layer, and nine devices utilizing a UV-opaque encapsulant barrier layer 225 in accordance with embodiments of the present invention.
• the reliability test was performed for a time period of 500 hours, and the devices were exposed to 55 °C and 85% humidity under 150 mA of applied current.
• three (i.e., 50%) of the devices exhibited complete failure, i.e., zero output power due to an open circuit (due to, e.g., broken wire bonds) due to crack formation in the transparent encapsulant.
• FIG. 4 is a plan-view photograph of a control device 400 without the barrier layer 225 or the non-encapsulant barrier 305 utilized in embodiments of the present invention.
• a UV LED chip 405 of the control device 400 is encased in a transparent encapsulant 410, in which cracks 415 have formed after only 255 hours of the reliability testing.
• FIG. 5 is a plan- view photograph of an exemplary packaged UV LED 500 with a barrier layer in accordance with embodiments of the present invention after the reliability testing.
• the packaged UV LED 500 of Figure 5 features a UV LED chip 505 surrounded by a UV-opaque encapsulant barrier layer 225. No cracks in the encapsulant formed for testing times of at least 500 hours.

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• 2015
  • 2015-04-06 US US14/679,655 patent/US9293670B2/en active Active
  • 2015-04-06 EP EP15776164.4A patent/EP3130011A4/en not_active Withdrawn
  • 2015-04-06 JP JP2016561774A patent/JP2017510997A/ja active Pending
  • 2015-04-06 WO PCT/US2015/024526 patent/WO2015157178A1/en not_active Ceased
  • 2015-04-06 CN CN201580012926.5A patent/CN106104821A/zh active Pending
• 2016
  • 2016-02-16 US US15/044,577 patent/US9548431B2/en not_active Expired - Fee Related
  • 2016-12-08 US US15/373,175 patent/US10383963B2/en active Active

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