Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L25/00—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof
  • H01L25/03—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes
  • H01L25/04—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers
  • H01L25/075—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group H01L33/00
  • H01L25/0753—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group H01L33/00 the devices being arranged next to each other
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
  • H01L33/50—Wavelength conversion elements
  • H01L33/505—Wavelength conversion elements characterised by the shape, e.g. plate or foil
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
  • H01L33/64—Heat extraction or cooling elements
  • H01L33/644—Heat extraction or cooling elements in intimate contact or integrated with parts of the device other than the semiconductor body
• • 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

Definitions

• the present disclosure relates to light emitting diode (LED) lighting devices and, more particularly, packaged chip-on-board (COB) LED arrays.
• LED light emitting diode
• COB packaged chip-on-board
• high brightness LED lighting devices i.e., light sources approaching or exceeding 1000 lumens, typically require a significant number of blue LEDs 10 configured in a two-dimensional array that is secured, for example, to a metal clad PC board 20.
• the diode array is covered by a color conversion phosphor dispersed in a silicone encapsulant 30.
• COB LED arrays are becoming standardized in shape, light output, and electrical drive requirements and could conceivably become the new lighting standard.
• the present inventors have recognized that a significant metric for packaged chip-onboard (COB) LED arrays is light output, measured in lumens per LED, with the understood objective of maximizing light output per LED while minimizing cost per LED.
• Light output per LED is, however, limited by the temperature rise of the phosphor and the impact of that rise on the surrounding silicone. Due to the inherent conversion inefficiency of the phosphor as well as Stokes shift during color conversion, some of the blue light is converted into heat, which can be removed by thermal conduction through the LED to an underlying heat sink.
• the silicone potting compound in which the phosphor is mixed has a relatively low thermal conductivity- a condition that can cause a significant temperature rise in the phosphor-in-silicone film.
• the temperature of the phosphor- in-silicone film can reach 160 degrees, which is the maximum operating temperature of the silicone but typically does not correspond to the maximum light output or temperature of the LED. Accordingly, the present disclosure introduces means by which heat can be more efficiently removed from the color converting layer of an LED lighting device to allow the LED(s) of the device to be driven harder, increasing total light output.
• packaged chip- on-board (COB) LED arrays are provided where a color conversion medium is distributed within a glass containment plate, rather than silicone, to reduce the operating temperature of the color conversion medium and avoid damage while increasing light output.
• the glass containment plate may be provided as a glass containment frame comprising an interior volume for containing a color conversion medium, a glass containment matrix in which the color conversion is distributed, or any other substantially planar structural glass member, vessel, or assembly suitable for containing the color conversion medium.
• the glass containment plate loaded with the color conversion medium, sits just above the wire bonds of the LED array.
• Plain silicone can be used to surround the LEDs, rather than air, which is a poor thermal conductor. This means that the thickness of the silicone above the LEDs can be reduced to the height of the wire bonds, i.e., about 50 ⁇ with the very low profile variety of wire bonds.
• This structure is beneficial in a number of ways. First the color conversion medium can itself withstand higher temperature than cases where the medium is dispersed in silicone because the glass containment plate has no organic component. Further, the ability to channel heat to the heat sink of the packaged LED is greatly improved because the thickness of the silicone layer above the LEDs is greatly reduced, e.g., from about 750 ⁇ to about 50 ⁇ .
• the glass containment plate of the present disclosure is also beneficial because it provides for additional manufacturing process control. Specifically, the plate can be tested separately from the corresponding LED array and an appropriate plate-to-array pairing can be made to achieve the desired color output. This is not the case when a conversion medium is provided as a slurry in the silicone used to encapsulate the LED array.
• a lighting device comprising a chip-on-board (COB) light emitting diode (LED) light source, a light source encapsulant, a distributed color conversion medium, and a glass containment plate.
• COB chip-on-board
• LED light emitting diode
• the COB LED light source comprises a thermal heat sink framework and at least one LED and defines a light source encapsulant cavity in which the light source encapsulant is distributed over the LED.
• the glass containment plate is positioned over the light source encapsulant cavity and contains the distributed color conversion medium.
• the light source encapsulant is distributed over the LED at a thickness that is sufficient to encapsulate the LED and define encapsulant thermal conduction paths T PE (see Fig. 2) extending through the light source encapsulant to the thermal heat sink framework from the distributed color conversion medium.
• the glass containment plate comprises a glass matrix and the distributed color conversion medium comprises a phosphor distributed in the glass matrix.
• the distributed color conversion medium comprises a quantum dot structure contained within an interior volume of the glass containment plate.
• the distributed color conversion medium comprises a phosphor distributed in a glass matrix and the lighting device further comprises a quantum dot plate disposed over the glass containment plate to define a supplemental emission field of the lighting device.
• Fig. 1 illustrates an LED lighting device employing a phosphor-in-silicone color conversion medium
• FIG. 2 is a schematic illustration of an LED lighting device according to one embodiment of the present disclosure
• FIG. 3 is a schematic illustration of an LED lighting device according to another embodiment of the present disclosure.
• FIG. 4 is a schematic illustration of an LED lighting device according to yet another embodiment of the present disclosure.
• Figs. 2-4 illustrate COB LED lighting devices 100, 100', 100" that comprise at least one LED 110, a light source encapsulant 120, a distributed color conversion medium 130, a glass containment plate 140, 140', and a thermal heat sink framework 150 in the form of, for example, a metal clad printed circuit board.
• the color conversion medium 130 is distributed in two dimensions over an emission field of the LED lighting device within the glass containment plate 140, 140' and may comprise, for example, a color converting phosphor or a quantum dot structure.
• the specific materials selected for the light source encapsulant 120, color conversion medium 130, glass containment plate 140, 140' and the thermal heat sink framework 150 can be gleaned from references like US PG Pub. No. 2012/0107622, which relates primarily to the use of color converting phosphors in LED lighting devices, US 2012/0175588, which relates to the use of light-converting, colloidal, doped semiconductor nanocrystals to provide monochromatic and white light sources based on LEDs, and US 7,723,744, which relates to light-emitting devices that incorporate one or more underlying LED chips or other light sources and a layer having one or more populations of nanoparticles disposed over the light source.
• the nanoparticles absorb some light emitted by the underlying source, and re-emit light at a different level. By varying the type and relative concentration of nanoparticles, different emission spectra may be achieved.
• the COB LED light source 100, 100', 100" defines a light source encapsulant cavity in which the light source encapsulant 120 is distributed over the array of LEDs 110.
• the glass containment plate 140, 140' is positioned over the light source encapsulant cavity, contains the distributed color conversion medium 130, and defines glassy thermal conduction paths T PG extending through the glass containment plate 140, 140' to the thermal heat sink framework 150 from the distributed color conversion medium 130.
• the light source encapsulant 120 is distributed over the array of LEDs 110 at a thickness that is sufficient to encapsulate the LEDs 110, including their wire bonds and any other LED hardware, and define encapsulant thermal conduction paths T PE extending through the light source encapsulant 120 to the thermal heat sink framework 150 from the distributed color conversion medium 130.
• the present disclosure introduces means by which heat can be more efficiently removed from the color converting layer of an LED lighting device and means that allow for a greater absolute temperature rise in the color converting layer. Both of these factors allow the LED(s) of the device to be driven harder, increasing total light output.
• the thickness of the light source encapsulant 120 is preferably tailored such that the thermal conduction paths Tp E extend less than approximately 100 ⁇ through the light source encapsulant 120. More preferably, it is contemplated that the thickness of the light source encapsulant can be tailored such that the thermal conduction paths T PE extend less than approximately 50 ⁇ through the light source encapsulant 120.
• the thermal performance of the structure may be expressed in terms of the thermal resistances of the heat paths T PG and T PE , both of which are illustrated schematically in Figs. 2-4.
• the relatively vertical heat path Tp E dominates, mostly because its path is shorter than that of T PG .
• the thermal resistance of the traditional phosphor-insilicone LED structure of Figure 1 is approximately 5 times greater than the phosphor-in-glass design illustrated in Fig. 2.
• the relatively thin glass encapsulant matrix design of Fig. 2 reduces the temperature rise of the phosphor fivefold at comparable LED powers, which enables the LEDs to be driven at higher currents to produce more light. This advantage stems predominantly from the thin profile of the glass containment plate 140 and the reduced thickness of the encapsulant layer 120 above the LEDs 110.
• the thickness of the light source encapsulant 120 can be tailored such that the thermal conduction paths T PE encounter a thermal resistance of less than approximately 1/5 that of a traditional phosphor in silicone package, such as that depicted in Fig . 1. In one embodiment, this thermal resistance is less than approximately 15°C/W through the light source encapsulant 120.
• the glass containment plate 140 comprises a glass matrix and the distributed color conversion medium 130 comprises a phosphor distributed in the glass matrix, as disclosed in US PG Pub 2012/0107622 Al.
• the LED lighting device 100 further comprises a glass cover plate 145 disposed over the glass matrix, with ion exchanged glass being a suitable contemplated glass composition choice for the glass cover plate 145.
• the glass containment plate 140 can be permanently bonded to the glass cover plate 145 during firing of the two, to consolidate the frit of the glass containment plate 140.
• the glass containment plate 140 is provided as a glass containment matrix in which the color conversion medium 130 is distributed, it will be advantageous to provide the glass containment plate 140 by tape casting the material of the glass containment plate to a glass substrate and then bonding that substrate to the cover glass plate 145, which occurs during consolidation of the frit.
• the material of the glass containment plate 140 may be tape cast directly onto the cover glass plate 145, thus avoiding the need to bond the glass containment plate 140 to the cover glass plate 145.
• the LED lighting device 100' further comprises a quantum dot plate 160 disposed over the glass containment plate 140 to define a supplemental emission field of the LED lighting device 100'.
• the quantum dot plate 160 comprises a quantum dot structure 170 that is contained within an interior volume defined between opposing, sealed glass panels 160a, 160b of the quantum dot plate 160.
• the primary emission field that is defined by the distributed phosphor color conversion medium 130 is spatially congruent with, but spectrally distinct from, the supplemental emission field defined by the quantum dot plate 160. In this manner, the emission spectrum of the emission field defined by the quantum dot plate 160 can be tailored to add optical warmth to the emission spectrum of the emission field defined by the distributed phosphor color conversion medium 130.
• the quantum dots of the quantum dot plate can be tailored to add warmth by converting some of the yellow light, as well as leaking blue light, to red - one advantage being that red quantum dots have a relatively narrow emission band, unlike red phosphors which waste light by tailing into the IR. In the case of red quantum dots, since quantum dots have a relatively narrow emission band, the issue of tailing into the IR can be avoided thus preserving good power efficiency.
• the sizes of the quantum dots contained can be adjusted to obtain the desired color. It is also contemplated that a variety of quantum dot sizes can also be blended to obtain a particular color, e.g., white.
• the glass containment plate 140 and the quantum dot plate 160 must be made separately because the process of tape casting and firing the glass containment plate onto the quantum dot plate 160 would damage the quantum dot structure. For this reason, a separate thin silicone bond 135 is required between the quantum dot plate 160 and the glass containment plate 140.
• the glass containment plate 140' is presented in the form of a glass containment frame comprising an interior volume defined between opposing, sealed glass panels 140a, 140b for containing the distributed color conversion medium 170.
• the distributed color conversion medium 170 may be provided in the form of the quantum dot structure described above with reference to Fig. 3.
• the distributed color conversion medium 170 may comprise a quantum dot structure contained within an interior volume defined by opposing glass panels 140a, 140b, with flexible fusion glass being a suitable contemplated glass composition choice.
• the cover glass plate 145 of Fig. 2 is eliminated because the glass containment plates 140', 160', i.e., the quantum dot plates, can serve as the protective cover glass.
• the opposing, sealed glass panels comprise one cavity glass 140a, 160a and one sealing glass 140b, 160b.
• the sealing glass 140b, 160b is typically a relatively thin (about 100 ⁇ ) display grade glass, such as Willow which is a very thin (typically 100 ⁇ ) version of EAGLE XG® display glass available from Corning, Incorporated.
• a suitable cavity can be provided in the cavity glass 140a, 160a by any conventional or yet to be developed glass molding or glass machining technique including, for example, micromachining, laser-assisted machining or milling, laser ablation, etching, or combinations thereof. Sputtered glass can then be deposited on the underside of the sealing glass 140b, 160b and a laser can be used to peripherally bond the sealing glass 140b, 160b to the cavity glass while the quantum dots are resting in the cavity.
• sealed glass panels for containing the aforementioned quantum dots may be constructed by providing a relatively low melting temperature (i.e., low Tg) glass sealing strip along a peripheral portion of a sealing surface of the sealing glass, the cavity glass, or both.
• a relatively low melting temperature (i.e., low Tg) glass sealing strip along a peripheral portion of a sealing surface of the sealing glass, the cavity glass, or both.
• the glass sealing strip may be deposited via physical vapor deposition, for example, by sputtering from a sputtering target.
• a focused laser beam can be used to locally melt the low melting temperature glass sealing strip adjacent glass substrate material to form a sealed interface.
• the laser can be focused through either the cavity glass or the sealing glass and then positionally scanned to locally heat the glass sealing strip and adjacent portions of the cavity glass and sealing glass .
• the glass sealing strip is preferably at least about 15% absorbing at the laser processing wavelength.
• the cavity glass and the sealing glass are typically transparent (e.g., at least 50%, 70%, 80% or 90% transparent) at the laser processing wavelength.
• a blanket layer of sealing (low melting temperature) glass can be formed over substantially all of a surface of sealing glass.
• An assembled structure comprising the cavity glass/sealing glass layer/sealing glass can be assembled as above, and a laser can be used to locally-define the sealing interface between the two substrates.
• Laser 500 can have any suitable output to affect sealing.
• An example laser is a UV laser such as a 355 nm laser, which lies in the range of transparency for common display glasses.
• a suitable laser power can range from about 5 W to about 6.15 W.
• a translation rate of the laser i.e., sealing rate
• the laser spot size can be about 0.5 to 1 mm.
• the width of the sealed region which can be proportional to the laser spot size, can be about 0.1 to 2 mm, e.g., 0.1, 0.2, 0.5, 1, 1.5 or 2 mm.
• a total thickness of a glass sealing layer can range from about 100 nm to 10 microns. In various embodiments, a thickness of the layer can be less than 10 microns, e.g., less than 10, 5, 2, 1, 0.5, or 0.2 microns.
• Example glass sealing layer thicknesses include 0.1, 0.2, 0.5, 1, 2, 5 or 10 microns.
• the material of the glass sealing strip is transparent and/or translucent, relatively thin, impermeable, "green,” and configured to form hermetic seals at low temperatures and with sufficient seal strength to accommodate large differences in CTE between the sealing material and the adjacent glass substrates. Further, it may be preferable to ensure that the material of the sealing strip is free of fillers, binders, and/or organic additives.
• the low melting temperature glass materials used to form the sealing material may or may not be formed from glass powders or ground glass.
• suitable sealing materials include low T g glasses and suitably reactive oxides of copper or tin.
• the glass sealing material can be formed from low T g materials such as phosphate glasses, borate glasses, tellurite glasses and chalcogenide glasses.
• a low T g glass material has a glass transition temperature of less than 400°C, e.g., less than 350°C, 300°C, 250°C, or 200°C.
• Example borate and phosphate glasses include tin phosphates, tin fluorophosphates, and tin fluoroborates.
• Sputtering targets can include such glass materials or, alternatively, precursors thereof.
• Example copper and tin oxides are CuO and SnO, which can be formed from sputtering targets comprising pressed powders of these materials.
• glass sealing compositions can include one or more dopants, including but not limited to tungsten, cerium and niobium.
• dopants can affect, for example, the optical properties of the glass layer, and can be used to control the absorption by the glass layer of laser radiation. For instance, doping with ceria can increase the absorption by a low T g glass barrier at laser processing wavelengths.
• Example tin fluorophosphate glass compositions can be expressed in terms of the respective compositions of SnO, SnF 2 and P 2 0 5 in a corresponding ternary phase diagram.
• Suitable tin fluorophosphates glasses include 20-100 mol% SnO, 0-50 mol% SnF 2 and 0-30 mol% P 2 0 5 .
• These tin fluorophosphates glass compositions can optionally include 0-10 mol% W0 3 , 0-10 mol% Ce0 2 and/or 0-5 mol% Nb 2 0 5 .
• a composition of a doped tin fluorophosphate starting material suitable for forming a glass sealing layer comprises 35 to 50 mole percent SnO, 30 to 40 mole percent SnF 2 , 15 to 25 mole percent P 2 0 5 , and 1.5 to 3 mole percent of a dopant oxide such as W0 3 , Ce0 2 and/or Nb 2 0 5 .
• a tin fluorophosphate glass composition is a niobium-doped tin oxide/tin fluorophosphate/phosphorus pentoxide glass comprising about 38.7 mol% SnO, 39.6 mol% SnF 2 , 19.9 mol% P 2 0 5 and 1.8 mol% Nb 2 0 5 .
• Sputtering targets that can be used to form such a glass layer may include, expressed in terms of atomic mole percent, 23.04% Sn, 15.36% F, 12.16% P, 48.38% 0 and 1.06% Nb.
• a tin phosphate glass composition according to an alternate embodiment comprises about 27% Sn, 13% P and 60% 0, which can be derived from a sputtering target comprising, in atomic mole percent, about 27% Sn, 13% P and 60% 0.
• the various glass compositions disclosed herein may refer to the composition of the deposited layer or to the composition of the source sputtering target.
• example tin fluoroborate glass compositions can be expressed in terms of the respective ternary phase diagram compositions of SnO, SnF and B 0 3 .
• Suitable tin fluoroborate glass compositions include 20-100 mol% SnO, 0-50 mol% SnF 2 and 0-30 mol% B 0 3 .
• These tin fluoroborate glass compositions can optionally include 0-10 mol% W03, 0-10 mol% Ce0 2 and/or 0-5 mol% Nb 2 0 5 .
• heat flow H (watts) is proportional to the associated temperature gradient, which in one dimension x is dT/dx.
• k is the thermal conductivity of the material and A is the cross-sectional area of an infinitesimal slab of thickness dx through which the heat flows. If the heat flow is confined to one dimension in an insulated thermal path, then the solution to equation 1 is simply
• th is defined as the thermal resistance and L is the length of the thermal path.
• the heat flow in the COB array is vertical from the phosphor through the thin ( ⁇ 5 ⁇ thick) GaN LED and the underlying sapphire substrate to the heat sink.
• the array can be modeled as a one-dimensional heat flow and calculate the thermal resistance using equation (2) above.
• about 1.3 watts is lost as heat in the phosphor, leaving about 3.7 watts total light output.
• the hottest plane in the package is the surface of the phosphor.
• the array can be modeled as two thermal resistances in series, i.e., the phosphor-in-silicone as the first thermal resistance and the sapphire LED substrate as the second thermal resistance.
• the GaN film is so thin, that its thermal resistance is negligible.
• the absorption depth d is about 0.3285 mm.
• the film should be as thin as possible to minimize the thermal resistance for heat flow from the phosphor-in- glass (PiG) film to the GaN heat sink and it is contemplated that a 50 ⁇ thickness should be enough to clear the LED wirebonds.
• a 50 ⁇ thickness should be enough to clear the LED wirebonds.

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• 2014
  • 2014-03-13 CN CN201480014703.8A patent/CN105453262A/zh active Pending
  • 2014-03-13 EP EP14721609.7A patent/EP2973699A1/de not_active Withdrawn
  • 2014-03-13 WO PCT/US2014/025418 patent/WO2014159894A1/en active Application Filing
  • 2014-03-13 KR KR1020157028982A patent/KR20150132354A/ko not_active Application Discontinuation
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