Light emitting diode component

In a lighting package, a printed circuit board supports at least one light emitting die. A light transmissive cover is disposed over the at least one light emitting die. A phosphor is disposed on or inside of the light transmissive dome-shaped cover. The phosphor outputs converted light responsive to irradiation by the at least one light emitting die. An encapsulant substantially fills an interior volume defined by the light-transmissive cover and the printed circuit board.

BACKGROUND

The present invention relates to the lighting arts. It especially relates to single-chip and multiple-chip light emitting diode components and methods for making same, and will be described with particular reference thereto. However, the invention applies to light emitting packages generally, and is applicable in packaging monolithic light emitting diode array dice, edge-emitting laser dice, vertical cavity light emitting dice or monolithic laser array dice, organic light emitting devices or organic light emitting array devices, and the like. The inventive light emitting packages and components will find application in substantially any application that employs one or more light sources.

Light emitting diode components provide illumination in small, rugged, reliable packages. Light emitting diodes have been developed in many colors spanning the visible spectrum and extending into the infrared and ultraviolet. While each light emitting diode typically emits light in a narrow spectral range, primary color light emitting diodes can be combined to emit white light. In another approach for generating white light, light from a blue, violet, or ultraviolet light emitting diode is coupled with a suitable phosphor to produce white light. Other colors can similarly be generated by suitable selection of light emitting die components, phosphors, and combinations of die components and phosphors.

One issue with light emitting diode components or packages relates to light output intensity. Early light emitting diodes had low light output intensities and were generally not competitive with incandescent and fluorescent light sources. Improvements in crystal growth, device fabrication, packaging methods, phosphor materials, and the like have substantially improved the light output intensities of modern light emitting diode packages. However, improvements in light output intensities are still being sought.

Another issue with light emitting diode components and packages relates to ruggedness. Commonly used packaging techniques, such as bonding of the dice to lead frames, can produce relatively fragile light emitting packages. Moreover, light emitting diode components and packages tend to be complex. A typical single-chip package may include, for example, a light emitting diode die, a lead frame, an encapsulant disposed over the light emitting diode die and a portion of the lead frame, and a phosphor embedded in the encapsulant.

Multiple chip packages generally further increase complexity. One example of such a multiple chip package is disclosed in Lowery, U.S. Pat. No. 6,504,301, which shows various arrangements involving generally wire-bonded interconnection of a plurality of light emitting dice disposed on a support placed in a housing including a cylindrical casing and a fluorescent plate. A similar multiple chip package is disclosed in Baretz et al., U.S. Pat. No. 6,600,175. Baretz discloses a phosphor contained in an encapsulant disposed inside the housing, The complexity of multiple chip packages such as those of Lowery and Baretz can adversely impact manufacturability, reliability, and manufacturing costs.

Another issue with typical light emitting diode packages and components is operating lifetime. Performance of packages employing phosphor wavelength conversion of ultraviolet or short-wavelength visible light typically degrades over time due to discoloration or other degradation of the encapsulant or other materials caused by the ultraviolet or short-wavelength visible light irradiation.

Another issue with typical light emitting diode packages is plug-in capability with lighting fixtures. A typical light emitting diode package is configured as a discrete electronic component and includes a lead frame or other electronic component mounting arrangement designed for solder connection. This approach is suitable for applications such as visual power indicators. For illumination, however, the light emitting diode package would desirably be used in a manner more analogous to a light bulb, fluorescent lighting tube, halogen bulb, or so forth, rather than as a discrete electronic component. To enable plug-in capability, the light emitting diode package for illumination applications should be readily connectable with existing illumination fixtures such as Edison sockets, track lighting fixtures, or so forth. Such plug-in fixture compatibility is, however, hampered by the typically high voltage and/or high frequency electrical power supplied by such fixtures, which is not conducive to powering low-voltage light emitting diode devices.

Another issue with using light emitting diode packages for illumination is light output quality. When light emitting diode packages employ several light emitting chips so as to produce high light intensity, a problem arises in that the output consists of several approximate point light sources corresponding to the several chips. This pixelated spatial distribution of light is problematic for illumination applications.

Spectral light output quality can also be an issue when using light emitting diode packages for white illumination. For example, different applications may call for different color rendering index (CRI) values. Obtaining white light or substantially white light with a desired (usually high) CRI value in a commercially practical manner is difficult. Existing cost-effective “white” phosphor compositions sometimes have relatively low CRI values.

The present invention contemplates improved apparatuses and methods that overcome the above-mentioned limitations and others.

BRIEF SUMMARY

According to one aspect, a light emitting package is disclosed. A printed circuit board supports at least one light emitting die and has at least two electrical terminals. Printed circuitry of the printed circuit board connects the at least one light emitting die with the at least two electrical terminals to provide power thereto. A light transmissive cover is disposed over the at least one light emitting die but not over the at least two electrical terminals. The cover has an open end defining a cover perimeter connected with the printed circuit board. An inside surface of the cover together with the printed circuit board defines an interior volume containing the at least one light emitting die. An encapsulant is disposed in the interior volume and covers at least the light emitting die.

According to another aspect, a light emitting package is disclosed. A support has at least one light emitting die disposed thereon. A glass cover is disposed on the support over the at least one light emitting die. The glass cover and the support cooperatively define an interior volume containing the at least one light emitting die. An encapsulant is disposed in the interior volume and encapsulates the at least one light emitting die.

According to another aspect, a light emitting package is disclosed. A support has at least one light emitting die disposed thereon. A single piece light transmissive cover is disposed on the support over the at least one light emitting die. The single piece cover and the support cooperatively define a substantially closed interior volume containing the at least one light emitting die. An encapsulant is disposed in the interior volume and encapsulates the at least one light emitting die.

According to another aspect, a method is provided for making a light emitting package. At least one light emitting die is electrically and mechanically connected to a printed circuit board. A light transmissive cover is secured to the printed circuit board. The light transmissive cover covers the at least one light emitting die. The secured light transmissive cover and the printed circuit board cooperatively define an interior volume. An encapsulant is disposed in the interior volume.

According to another aspect, a method is provided for disposing of a phosphor on a surface. An adhesive is disposed on the surface. A phosphor powder is applied to the adhesive. The adhesive is hardened.

According to another aspect, a lighting package is disclosed. A printed circuit board supports at least one light emitting die. A light transmissive cover is disposed over the at least one light emitting die. At least one phosphor composition comprising at least one phosphor compound is disposed on or inside of the light transmissive cover. The at least one phosphor composition outputs converted light responsive to irradiation by the at least one light emitting die.

According to another aspect, a lighting package is disclosed. A printed circuit board supports at least one light emitting die. A light transmissive cover is disposed over the at least one light emitting die. An encapsulant substantially fills an interior volume defined by the light-transmissive cover and the printed circuit board.

According to another aspect, a lighting package is disclosed. A printed circuit board supports at least one light emitting die. A light transmissive cover is disposed over the at least one light emitting die. Electrical power-conditioning circuitry is disposed on the printed circuit board and is configured to condition received input power to energize the supported at least one light emitting die.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

With reference toFIGS. 1-3, a light emitting package8includes a printed circuit board10on which one or more light emitting chips or die are disposed. The printed circuit board is preferably substantially thermally conductive. For example, a metal core printed circuit board can be employed. In the illustrated embodiment, three light emitting chips or dice12,14,16are disposed on the circuit board10; however, the number of dice can be one die, two dice, or more than three dice. The die or dice can be group III-nitride blue or ultraviolet light emitting diodes, red group III-phosphide or group III-arsenide light emitting diodes, II-VI light emitting diodes, IV-VI light emitting diodes, silicon or silicon-germanium light emitting diodes, or the like. As used herein, the term “ultraviolet” is intended to encompass light emitting diode emission having a peak wavelength less than or about 425 nm. In some contemplated embodiments, the die or dice are edge emitting lasers or vertical cavity surface emitting lasers. The light emitting chips or dice can also be organic light emitting diodes or devices. Each light emitting die or dice can be a bare die, or each die or dice can include an individual encapsulant. Still further, the die or dice can be a monolithic array of light emitting diode mesas, vertical cavity surface emitting laser mesas, or the like. In the illustrated embodiment, the dice12,14,16are disposed in corresponding reflective wells22,24,26; however, the die or dice may be mounted on a planar surface of the printed circuit board10or can be mounted on raised pedestals or other elevated support structures. In some embodiments, a portion or all of the side of the printed circuit board10on which the light emitting dice or chips12,14,16are disposed has a reflective layer disposed thereon to improve light extraction from the package8.

With particular reference toFIG. 3, the illustrated printed circuit board10includes one or more printed circuitry layers30sandwiched between insulative layers32,34. Typically, electrical pads are formed on the die attach surface of the printed circuit board10using appropriate vias passing through the insulative layer32to electrically connect the dice12,14,16with the printed circuitry30. The die or dice12,14,16can be mechanically and electrically attached to the printed circuit board10in various ways, such as: by flip-chip bonding of die electrodes to electrical pads of the printed circuit board10; by soldering the die to the board10and using wire bonds to electrically connect the die electrodes with electrical pads of the printed circuit board10; by soldering the die to a lead frame (not shown) that is in turn mounted to the printed circuit board10; or so forth. The die attachment can include a sub-mount (not shown) disposed between a light emitting die or chip and the printed circuit board or other support, or between the chip and a lead frame. In some embodiments, chip bonding is achieved using thermosonic bonding, thermocompressive bonding, ultrasonic bonding, eutectic bonding with or without underfill, or so forth. Still further, rather than mounting individual dice as illustrated herein, it is contemplated to employ a monolithic light emitting diode array formed on a common substrate. In this contemplated embodiment, the common substrate is soldered, thermosonically bonded, thermocompressively bonded, or otherwise secured to the printed circuit board10, and electrical connection to the individual light emitting mesas or structures is made by wire bonding, conductive traces formed on the common substrate, or the like. Alternatively, a monolithic array having a transparent common substrate can be configured for a flip-chip mounting in which the electrodes of the light emitting mesas or structures are directly bonded to electrical pads.

The printed circuit board10preferably further includes a heat sinking structure such as a ground plate or metal core38to provide heat sinking of the light emitting chips or dice12,14,16. Optionally, an insulative back-plate (not shown) is disposed on the side of the metal core38distal from the die attach surface. The heat sink is optionally omitted in lower power lighting packages, packages mounted on a heat sinking surface, or the like. Moreover, the printed circuitry layer or layers30may provide adequate heat sinking in some embodiments. In still yet other embodiments, the material or materials forming the insulative layers32,34are chosen to be thermally conductive so that these layers provide heat sinking.

The printed circuit board10optionally supports associated electrical components, such as a zener diode component44including one or more zener diodes connected across the light emitting dice12,14,16by the printed circuitry30to provide electrostatic discharge protection for the dice. Similarly, electrical power conversion circuitry, power regulating circuitry, voltage stabilizing circuitry, current-limiting circuitry, rectifying circuitry, various combinations thereof, or the like, can be included as additional components on the printed circuit board10. Such components can be provided as one or more discrete components, or as an application-specific integrated circuit (ASIC). Moreover, an electrical plug, adaptor, electrical terminals46, or the like can be disposed on the printed circuit board10. In some embodiments, it is contemplated to include more than one set of electrical terminals, for example to enable series, parallel, or series-parallel interconnection of a plurality of light emitting packages. The printed circuitry30includes traces connecting the electrical terminals46with the light emitting dice or chips12,14,16such that suitable electrical power applied to the electrical terminals46energizes the light emitting dice or chips12,14,16and associated circuitry (if any) such as the zener diode component44, voltage stabilizing circuitry, current limiting circuitry, or so forth. The printed circuit board10can include other features such as a mounting socket, mounting openings50,52or the like for mechanically installing or securing the light emitting package8.

The described printed circuit board10is an example. Other types of printed circuit boards or other support structures can also be employed. For example, the printed circuit traces can be disposed on the die attach surface and/or on the bottom surface rather than being sandwiched between insulative layers32,34. Thus, for example, the printed circuit board can be an electrically insulating support with a conductive trace evaporated and patterned or otherwise formed on the insulating support. Moreover, a heat sink can be substituted for the printed circuit board, for example with the light emitting die or dice soldered or otherwise mechanically secured to the heat sink and with the die electrodes wire bonded to electrical pads.

With continuing reference toFIGS. 1-3, the light emitting package8further includes a light transmissive cover60disposed over the light emitting dice or chips12,14,16. The light transmissive cover has an open end defining a cover perimeter62that connects with the printed circuit board10. In the illustrated embodiment, the printed circuit board10includes an optional annular groove66that receives the perimeter62of the light transmissive cover60, which in the light emitting package8is a hemispherical dome-shaped cover. The groove66guides in positioning the cover60on the printed circuit board10, and optionally also is used to help secure the cover to the board. In some embodiments the annular groove66is omitted, in which case the placement of the cover60on the printed circuit board10is positioned by other means, such as by using an automated assembly jig.

The light transmissive cover60can be secured to the printed circuit board10in various ways, such as by an adhesive, by a friction fit between the perimeter62and the groove66, by fasteners, or so forth. The light transmissive cover60together with the printed circuit board10define an interior volume70containing the light emitting dice or chips12,14,16. In some embodiments, the connection between the perimeter62of the light transmissive cover60and the printed circuit board10is a substantially airtight sealing connection that substantially hermetically seals the interior volume70. In other embodiments, the connection between the perimeter62and the printed circuit board10is not a hermetic seal, but rather may contain one or more gaps, openings, or the like.

A phosphor72(indicated by a dotted line inFIG. 3) is optionally disposed on an inside surface of the cover60. If provided, the phosphor is selected to produce a desired wavelength conversion of a portion or substantially all of the light produced by the light emitting dice or chips12,14,16. The term “phosphor” is to be understood as including a single phosphor compound or a phosphor blend or composition of two or more phosphor compounds chosen to produce a selected wavelength conversion. For example, the phosphor72may be a phosphor composition including red, green, and blue phosphor compounds that cooperatively provide white or substantially white light. In some embodiments, the tri-phosphor blend of (Ba,Sr,Ca)5(PO4)3Cl:Eu2+, Sr4Al14O25:Eu2+, and 3.5MgO*0.5MgF2*GeO2:Mn4+phosphors is used. In some embodiments, the phosphor compound (Ca,Sr,Ba)2Si1−cO4−2c:Eu2+where 0≦c<0.25 is used alone or in combination with other phosphor compounds, and the phosphor is excited by a light emitting diode die or chip emitting radiation having a peak emission from about 200 nm to about 500 nm. In some embodiments, the phosphor composition includes phosphor compounds (Ca,Sr,Ba)Al2O4:Eu2+, Sr4Al14O25:Eu2+, and (Ca,Sr,Ba)MgAl10O17:Eu2+,Mn2+. For purposes of the present application, it should be understood that when a phosphor has two or more dopant ions (i.e. those ions following the colon in the above compositions), this is meant to mean that the phosphor has at least one (but not necessarily all) of those dopant ions within the material. That is, as understood by those skilled in the art, this type of notation means that the phosphor can include any or all of those specified ions as dopants in the formulation. In some embodiments, the phosphor blend is selected to provide white light with color coordinates lying on or near the blackbody locus and a color temperature less than 4500K. In some embodiments, the phosphor blend is selected to provide white light with color coordinates lying on or near the blackbody locus and a color rendering index (Ra) of 90 or greater.

Some various suitable phosphor compounds that can be used alone as a single-compound phosphor composition and/or in combination with other phosphor compounds as a multiple-compound phosphor composition are listed here:(Mg,Ca,Sr,Ba,Zn)5(PO4)3Cl:Eu2+(Ca,Sr,Ba)2Si1−cO4−2c:Eu2+where 0≦c<0.25(Ba,Sr,Ca)5(PO4)3(Cl,F,Br,OH):Sb3+,Mn2+(Mg,Ca,Sr,Ba,Zn)5(PO4)3(F,Cl,Br,OH):Eu2+,Mn2+(Ba,Sr,Ca)BPO5:Eu2+,Mn2+(Sr,Ca)10(PO4)6*nB2O3:Eu2+Sr2Si3O8*2SrCl2:Eu2+Sr4Al14O25:Eu2+(Ca,Sr,Ba)MgAl10O17:Eu2+,Mn2+Ba3MgSi2O8:Eu2+BaAl8O13:Eu2+2SrO*0.84P2O5*0.16B2O3:Eu2+;(Ba,Sr,Ca)Al2O4:Eu2+(Y,Gd,Lu,Sc,La)BO3:Ce3+,Tb3+Ca8Mg(SiO4)4Cl2:Eu2+,Mn2+(Ba,Sr,Ca)2(Mg,Zn)Si2O7:Eu2+(Sr,Ca,Ba)(Al,Ga,In)2S4:Eu2+(Y,Gd,Tb,La,Sm,Pr,Lu)3(Al,Ga)5−fO12−3/2f:Ce3+(wherein 0≦f≦0.5)(Lu,Y,Sc)2−g(Ca,Mg)1+gLihMg2−h(Si,Ge)3−hPhO12−g:Ce3+(wherein 0≦g≦0.5, 0≦h≦0.5)(Ca,Sr)8(Mg,Zn)(SiO4)4Cl2:Eu2+,Mn2+Na2Gd2B2O7:Ce3+, Tb3+(Sr,Ca,Ba,Mg,Zn)2P2O7:Eu2+,Mn2+(Ca,Sr,Ba,Mg, Zn)10(PO4)6(F,Cl,Br,OH)2:Eu2+,Mn2+(Gd,Y,Lu,La)2O3:Eu3+,Bi3+(Gd,Y,Lu,La)2O2S:Eu3+,Bi3+(Gd,Y,Lu,La)VO4:Eu3+,Bi3+SrY2S4:Eu2+CaLa2S4:Ce3+(Ca,Sr)S:Eu2+(Ba,Sr,Ca)MgP2O7:Eu2+,Mn2+(Y,Lu)2WO6:Eu3+,Mo6+(Ba,Sr,Ca)uSiv(N,O)w:Eu2+(Lu,Ca,Li,Mg,Y)alpha-SiAlON doped with Eu2+and/or Ce3+(Y,Lu,Gd)2−tCatSi4N6+tC1−t:Ce3+(wherein 0≦t≦0.5)3.5MgO*0.5MgF2*GeO2:Mn4+A2[MF6]:Mn4+, where A=Li, Na, K, Rb or Cs and M=Ge, Si, Sn, Ti or ZrCa1−d−eCedEueAl1−d(Mg,Zn)dSiN3.
Those skilled in the art can readily select other phosphor compounds suitable for performing specific light conversions.

It should be noted that various phosphors are described herein in which different elements enclosed in parentheses and separated by commas, such as in the above Ca1−d−eCedEueAl1−d(Mg,Zn)dSiN3phosphor. As understood by those skilled in the art, this type of notation means that the phosphor can include any or all of those specified elements in the formulation in any ratio from 0 to 100%. That is, this type of notation, for the above phosphor for example, has the same meaning as Ca1−d−eCedEueAl1−d(Mg1−qZnq)dSiN3, wherein 0≦q≦1.

In some embodiments, a phosphor composition including phosphor compounds Sr4Al14O25:Eu2+and (Ca,Sr,Ba)MgAl10O17:Eu2+,Mn2+are employed to produce a green light suitable for use in application such as traffic signals. Similarly, other listed phosphors are also suitable for producing saturated colors and/or as phosphor compound components in white phosphor compositions.

In one embodiment, the light emitting dice or chips12,14,16are blue, violet, or ultraviolet emitters such as group III-nitride light emitting diodes, and the phosphor72converts most or substantially all of the light generated by the chips12,14,16into white light. In another embodiment the light emitting dice or chips12,14,16are blue light emitters such as group III-nitride light emitting diodes, and the phosphor72is a yellow phosphor that converts some of the blue light into yellow light wherein direct blue light and indirect yellow phosphor-generated light combine to produce white light. In yet another embodiment the light emitting dice or chips12,14,16are blue, violet, or ultraviolet emitters and the phosphor72converts most or substantially all of the emitted light into light of a selected color, such as green, yellow, red, or so forth, so that the light emitting package8produces a colored light. These are examples only, and substantially any down-conversion of light produced by the light emitting dice or chips12,14,16can be performed by suitable selection of light emitting dice or chips12,14,16outputting at a selected wavelength and suitable selection of the phosphor72. In some embodiments, the phosphor72is omitted and the direct light produced by the light emitting diodes12,14,16is the light output of the light emitting package.

In some embodiments, the light transmissive cover60is a glass cover, where “glass” is not limited to silica-based materials but rather encompasses substantially any inorganic, amorphous light transmissive material. Making the cover60of glass has certain advantages over plastic or other organic covers. Glass typically has better thermal stability than most plastics. Glass is more readily coated with optical coatings such as wavelength-selective reflective coatings, wavelength-selective absorbing coatings, or the like. Glass is also typically more resistant to scratching compared with most plastics. Moreover, glass has particular advantages in embodiments in which the light emitting dice or chips12,14,16produce ultraviolet or short-wavelength visible light, because light at these wavelengths can discolor or otherwise degrade the optical quality of light transmissive plastics over time. Optionally, a glass is selected which provides high reflectivity or absorption in the ultraviolet. In other embodiments, the light transmissive cover60is made of plastic, Teflon, epoxy, EVA, acrylic, or another organic light transmissive material. In yet other contemplated embodiments, the cover60is made of a crystalline light transmissive material such as crystalline quartz. Such crystalline covers typically share many of the advantages of glass covers.

The printed circuit board10can include various reflective coatings or reflective surfaces for improving light extraction efficiency. In some embodiments, substantially the entire surface of the printed circuit board on which the light emitting dice or chips12,14,16and the cover60are disposed is reflective for both light produced by the light emitting chips and for light produced by the phosphor72. In other embodiments, that portion or area of the printed circuit board surface covered by the cover60is reflective for both light produced by the light emitting chips and for light produced by the phosphor72, while that portion or area of the printed circuit board surface outside of the cover60is reflective principally for light produced by the phosphor72. These latter embodiments are suitable when substantially all of the direct light produced by the light emitting dice or chips12,14,16is converted by the phosphor, so that the output light is substantially entirely due to the phosphor. By using different reflective coatings or surfaces inside of and outside of the cover60, each reflective coating or surface can be independently optimized for the spectrum of light which it is intended to reflect.

It will be appreciated that the term “light transmissive” as used herein to describe the cover60refers to the desired light output produced by the light emitting package8. The light output includes light generated by the phosphor72, if present, responsive to irradiation by the light emitting dice or chips12,14,16. In some embodiments, the light output includes a portion or all of the direct light produced by the light emitting dice or chips12,14,16. Examples of the latter embodiments are a white light in which the white output light is a blending of blue light emitted by the light emitting dice or chips12,14,16and yellow light emitted by the phosphor72, or embodiments in which the phosphor72is omitted entirely. Where the direct light produced by the light emitting dice or chips12,14,16contributes to the output light, the cover60should be at least partially light transmissive for that direct light. In embodiments where the output light is solely produced by the phosphor72, on the other hand, the cover60may be light transmissive for the phosphor output but partially or wholly reflective or absorbing for the direct light produced by the light emitting dice or chips12,14,16.

An example of such a light emitting package is a white light emitting package in which the output white light is produced by the phosphor72responsive to ultraviolet light produced by the light emitting dice or chips12,14,16. The term “ultraviolet” is intended to encompass light produced by the light emitting dice or chips12,14,16whose peak wavelength is less than or about 425 nm. In such embodiments, including both an ultraviolet-reflective coating on the cover60and an ultraviolet-reflective coating on the printed circuit board10can effectively retain ultraviolet light produced by the ultraviolet light emitting diodes within the interior volume70so that the ultraviolet light has multiple opportunities through multiple reflections to interact with the phosphor72, thus enhancing the ultraviolet-to-white light conversion efficiency. For retaining light, disposing the ultraviolet reflective coating on the inside of the cover60is advantageous to avoid ultraviolet absorption losses in the cover60. Alternatively, the ultraviolet reflecting coating can be disposed on the outside of the cover60, or as an embedded layer or thin region within the cover60.

The phosphor72can be applied to the inside surface of the light transmissive cover60using a suitable phosphor coating process, such as for example, electrostatic coating, slurry coating, spray coating, or so forth. Moreover, the phosphor can be disposed elsewhere besides on the inside surface of the cover60. For example, the phosphor can be applied to the outside surface of the cover60, using for example spray coating, outer surface coating, or the like, or to both the inside and outside surfaces of the cover60. In yet another embodiment, the phosphor is embedded in the material of the light transmissive cover60. However, phosphor is not readily embedded into most glass or crystalline materials. In some embodiments the phosphor is disposed in a glass binder that is spun onto or otherwise coated onto the inside and/or outside surface of the cover60.

In one suitable phosphor application process, the inside surface of the cover60is prepared by treatment with a liquid or low viscosity semi-solid material acting as a glue. The liquid material can be, for example, liquid epoxy or silicone. The glue material can be applied in a variety of ways, such as by spraying, brushing, or dipping of its working formulation or a solution thereof in a suitable solvent such as acetone, methyl isobutyl ketone (MIBK), or t-butyl acetate. The phosphor is then deposited by dusting, dipping or pouring of phosphor in powder form, the choice of deposition method being based on the nature of the inside surface of the cover60. For example, pour phosphor powder is suitably poured into the concave inside surface of the cover60. On the other hand, dipping is generally a better method for coating the outside surface of the cover60. The glue is then hardened by solvent evaporation, thermal or UV curing, or the like to form the phosphor layer.

Repetitions or various combinations of the above-described example phosphor deposition and hardening processes may be performed, for example to deposit more than one layer of phosphor or multiple layers of phosphor blends, or as needed to attain a required thickness or layered phosphor structure. Optionally, the phosphor coating may be covered with a final layer of clear glue or other suitable material to provide mechanical protection, to filter out ambient ultraviolet light or excess radiation from the light emitting dice12,14,16, or so forth.

As noted previously, the light transmissive cover60optionally includes one or more optical coatings besides the phosphor72. In some embodiments, an anti-reflective coating is applied to the inside and/or outside surface of the cover60to promote light transmission. In embodiments in which the direct light produced by the light emitting dice or chips12,14,16does not form part of the output light, the light transmissive cover60optionally includes a wavelength-selective reflective coating to reflect the direct light back into the interior volume70where it has additional opportunity to interact with the phosphor72.

In preferred embodiments, the light transmissive cover60is a single piece cover, such as a single piece glass cover, a single piece molded plastic cover, or the like. Manufacturing the cover60as a single piece simplifies assembly of the lighting package8. Another advantage of a single piece cover60is that a substantially hermetic sealing of the interior volume70is obtained by ensuring a substantially hermetic seal between the perimeter62of the cover60and the printed circuit board10. The light transmissive cover60can include facets, fresnel lens contours, or other light refractive features that promote light scattering to produce a more spatially uniform light output. Similarly, the light transmissive cover60can be made of a frosted glass that has been etched with sand or the like to produce light scattering. Optionally, the cover60includes an anti-shatter coating such as CovRguard™ (available from General Electric Company, GE Lighting Division, Nela Park, Cleveland, Ohio), Teflon, urethane, vinyl, or so forth.

With particular reference toFIG. 3, the interior volume70is, in the lighting package8, substantially filled with an encapsulant76. The encapsulant76can be, for example, a silicone encapsulant, an epoxy encapsulant, or the like. The encapsulant76is at least partially light-transmissive or substantially transparent to light produced by the light emitting dice or chips12,14,16and acts as a refractive index-matching material promoting light extraction out of the light emitting dice or chips12,14,16, and preferably also promoting light coupling with the phosphor72and, if the direct light produced by the light emitting dice12,14,16directly contributes to the package light output, also preferably promotes light transmission into the cover60.

In some embodiments, the phosphor is dispersed in a binding material that is the same material as the encapsulant76. In other embodiments the phosphor-binding material is a different material that has a good refractive index match with the encapsulant76. In yet other embodiments, the encapsulant76serves as the binding material for the phosphor72. It will be appreciated that while the phosphor72is shown inFIG. 3as residing substantially along the inside surface of the cover60, in some embodiments the phosphor72may extend some distance away from the inside surface of the cover60and into the encapsulant76disposed in the interior volume70. In some contemplated embodiments, the phosphor is dispersed substantially into the encapsulant76, and may even be uniformly distributed throughout the encapsulant76. However, as described in International Publication WO 2004/021461 A2, there are efficiency advantages to spatially separating the phosphor from the light emitting dice or chips. Hence, in preferred embodiments the phosphor is disposed on the inside surface of the cover60, or is disposed closer to the cover60than to the light emitting dice or chips12,14,16. In some embodiments, light-scattering particles, particulates, or so forth are dispersed in the encapsulant76to provide more uniform light distribution.

In embodiments in which the light emitting dice or chips12,14,16are bare dice, that is, are not individually encapsulated, the encapsulant76provides a common encapsulation of the light emitting dice or chips12,14,16which protects the chips from damage due to exposure to moisture or other detrimental environmental effects. The encapsulant76may also provide potting of the light emitting dice or chips12,14,16to improve the robustness of the lighting package8and make the lighting package8more resistant to damage from vibrations or other mechanical disturbances.

In some embodiments the cover60is sealed to the printed circuit board10, and the encapsulant76is injected into the interior volume70after the light transmissive cover is sealed. To enable encapsulant injection, openings80,82are provided in the printed circuit board10. Alternatively, openings can be provided in the light transmissive cover or at the interface between the perimeter of the cover and the printed circuit board. At least two such openings80,82are preferably provided, so that while encapsulant material is injected into one opening displaced air can exit via another opening. In other embodiments, a single elongated or otherwise enlarged opening is used to provide room for both the inflowing encapsulant and the outflowing displaced air.

In embodiments in which the interior volume70is substantially hermetically sealed, the injected encapsulant76can be a liquid or non-rigid semi-solid encapsulant, such as an optical gel, that is contained by the hermetically sealed interior volume70. The liquid or non-rigid semi-solid encapsulant may be left uncured in some embodiments, since the hermetic seal prevents leakage of the encapsulant. Moreover, a hermetic seal optionally allows the encapsulant to be injected under some pressure, so that the encapsulant is at a pressure higher than atmospheric pressure. In some embodiments, the interior volume70is not hermetically sealed, and some of the injected encapsulant material may leak out. It will be appreciated that for encapsulant material of reasonably high viscosity, the amount of leaked encapsulant material is limited, and such leaked encapsulant material may even be advantageous insofar as it may help seal the interior volume70when the injected encapsulant is cured or otherwise hardened into a solid.

With continuing reference toFIGS. 1-3and with further reference toFIG. 4, an example process100for manufacturing the lighting package8is described. The light emitting dice or chips12,14,16are mechanically and electrically connected with the printed circuit board10in a die attach process102. The die attach can involve flip chip bonding, soldering, wire bonding, or so forth. Separately, the inside surface (and/or optionally the outside surface) of the light transmissive cover60is coated with the phosphor72, if such phosphor is included in the package8, in a phosphorizing process104. As used herein, the term “phosphorizing” denotes any method for putting a phosphor into the lighting package, such as coating or spraying a phosphor composition or compositions onto the light-transmissive cover, suspending phosphor particles in the encapsulant, embedding a phosphor in the light-transmissive cover, or so forth. In embodiments in which the cover has the phosphor embedded therein, the phosphorizing process104is omitted and instead the phosphor is incorporated during molding or other formation of the cover60. The cover is then secured, optionally sealed, to the printed circuit board10in a sealing process106. The sealing process106defines the interior volume70, which is optionally a hermetically sealed volume. The encapsulant76is then injected into the interior volume70through the openings80,82in an encapsulant injection process108. The encapsulant is cured in a curing process110if the encapsulant material requires curing. After injection and optional curing of the encapsulant76, the openings80,82are optionally sealed with a suitable sealing material in a sealing process112. In some embodiments, the encapsulant76also seals the openings80,82, and so in these embodiments the separate sealing process112is omitted.

With reference toFIG. 5, another lighting package8′ includes a printed circuit board10′ and a light transmissive cover60′ having an open end defining a cover perimeter62′, which are illustrated inFIG. 5and correspond to the printed circuit board10, cover60, and cover perimeter62′, respectively, of the lighting package8. The lighting package8′ also includes most other components of the lighting package8which however are not visible in the outside perspective view ofFIG. 5. The lighting package8′ differs from the lighting package8ofFIGS. 1-3in that the electrical terminals46of the lighting package8are replaced in the lighting package8′ by four electrical terminals46′ disposed on the backside of the printed circuit board10′. The electrical terminals46′ are electrically connected with the light emitting die or dice disposed in the cover60′ by suitable printed circuitry residing in or on the printed circuit board10′. The backside electrical terminals46′ can be configured, for example, to insert into matching openings of a four-prong surface-mount receptacle socket.

With returning reference toFIGS. 1-3, in some embodiments the phosphor composition72includes a mixture of at least two constituent phosphor compositions each possessing essentially the same emission color coordinates (for example x and y coordinates on the 1931 CIE chromaticity diagram) but different color rendering index (CRI) values. The at least two different constituent phosphor compositions are different in that they differ by at least one phosphor compound. For example, the first constituent phosphor composition may include blue, green, and yellow phosphor compounds A, B, and C, respectively, with a stoichiometry producing white or substantially white light at a first CRI value; the second constituent phosphor composition may include green, yellow, and red phosphor compounds B, C, and D, respectively, with a stoichiometry producing white or substantially white light at a second, different CRI value. In some embodiments, the blue, green, yellow, and red phosphor compounds A, B, C, and D are respectively (Ba,Sr,Ca)5(PO4)3Cl:Eu2+, Sr4Al14O25:Eu2+, (Ca,Sr,Ba)2Si1−cO4−2c:Eu2+where 0≦c<0.25, and 3.5MgO*0.5MgF2*GeO2:Mn4+. The output converted light consisting of a blending of the constituent converted light of the first and second phosphor compositions has a CRI value that is different from, and possibly larger than, the first or second CRI value of the individual constituent phosphor compositions.

With reference toFIG. 6, which plots the 1931 CIE diagram with the blackbody locus BB superimposed thereon, the first phosphor composition (A,B,C) can have stoichiometries whose color coordinates span a triangle having as vertices the color points of the phosphor compounds A, B, and C. The second phosphor composition (B,C,D) can have stoichiometries whose color coordinates span a triangle having as vertices the color points of the phosphor compounds B, C, and D. A cross-hatched triangle having as vertices the color points of the common phosphor compounds B and C and a third vertex E denote the range of color coordinates that can be achieved using suitable stoichiometries of either phosphor composition (A,B,C) or phosphor composition (B,C,D). In this range, CRI tuning and/or luminosity tuning is achievable by blending or combining the first and second phosphor compositions with stoichiometries corresponding to about the same color point. This approach enables CRI tuning by selecting the ratio of the first (A,B,C) constituent phosphor composition and second (B,C,D) constituent phosphor composition. More generally, at any given color point target, at least two constituent phosphor compositions are prepared, each constituent phosphor composition producing constituent converted light at substantially the same color point responsive to irradiation by emission of the light emitting die or chip612(preferably but not necessarily in the ultraviolet range, such as peak chip emission wavelength less than or about 425 nm). The number of phosphor compounds per constituent phosphor composition can be anywhere from one (such as, for example, suitable phosphor compounds disclosed in U.S. Pat. No. 6,522,065) to two, three or more (such as, for example, suitable phosphor blends disclosed in U.S. Pat. No. 6,685,852). The disclosures of U.S. Pat. Nos. 6,522,065 and 6,685,852 are incorporated by reference herein in their entirety. To minimize color point variation, the at least two different constituent phosphor compositions should preferably provide substantially the same color point when excited by emission of the light emitting die or chip612, preferably to within about 0.020 units in both x and y color coordinates on the 1931 CIE chromaticity diagram, more preferably to within 0.010 units, and still more preferably to within 0.005 units. In some embodiments, the amount of the two constituent phosphor compositions relative to each other is selected to optimize the light output respective to color rendering index (CRI) at a given minimal luminosity threshold, or vice versa, at a selected color point.

By varying the ratio or blending of two or more constituent phosphor compositions of substantially the same color point but different CRI values, one can alter the final CRI and luminosity characteristics of the device in a continuous fashion. By using a mixture of the constituent phosphor compositions, a continuous range of CRI values are achievable. For some such mixtures, the CRI value of the blended light may be larger than the CRI value of any of the constituent phosphor compositions acting alone. Advantageously, the CRI (e.g. maximize it for a given minimal luminosity requirement) or the luminosity (e.g. maximize it for a given minimal CRI requirement) of the lighting device608is tunable without affecting the chemical makeup of either the phosphor compounds or the constituent phosphor compositions configured for the color point target. This affords a set of at least two constituent phosphor compositions to be used for the manufacturing of white light sources with the same or similar color point but with CRI or luminosity values customized for specific applications. Some suitable approaches for optimizing or selecting the CRI using two or more constituent phosphor compositions having about the same color coordinates are disclosed in co-pending application Ser. No. 10/909,564 filed Nov. 2, 2004 which is incorporated by reference herein in its entirety. In some embodiments, the at least two different constituent phosphor compositions are selected to provide white light with color coordinates lying on or near the blackbody locus and a color temperature less than 4500K.

With reference toFIG. 7, in some embodiments, the at least two different constituent phosphor compositions are selected to blend to produce white light with a color rendering index (Ra) of 90 or greater. ExampleFIG. 7shows a CRI-tuned converted light spectrum using a mixture of the aforementioned (A,B,C) and (B,C,D) phosphor compositions that provided a correlated color temperature of about 3300K and a CRI value of about 90. When the blue or bluish bleed-through direct light emitting die radiation blending with the converted light spectrum ofFIG. 7is also accounted for, the color temperature was about 3500K and the CRI value was about 91. Higher or lower CRI values are attainable at the same color point or another color point attainable by both phosphor compositions by varying the ratio of the phosphor compositions, by using a technique such as Design of Experiment (DOE).

It is to be appreciated that the CRI-tuning mixture of phosphor compositions (A,B,C) and (B,C,D) is an example. Other mixtures can be used so long as the constituent phosphor compositions produce converted light at about the same color point of interest. In some CRI tuned embodiments, the constituent phosphor compositions each produce constituent converted light which is white light or substantially white light, that is, which lies on or substantially on the black body locus of the 1931 CIE chromaticity diagram. Such constituent phosphor compositions are suitably operated in conjunction with one or more ultraviolet light emitting chips or dice, that is, with chips or dice that emit peak radiation below or about at 425 nm. In these embodiments, the bleed-through light produced by the at least one light emitting die has a negligible contribution to the visible spectrum of the converted light of the different phosphor compositions blended with bleed-through light produced by the at least one light emitting die. This negligible contribution can result from an arrangement in which the conversion efficiency of the light produced by the at least one light emitting die is close to 100%. This negligible contribution can also result from the at least one light emitting die emitting light substantially outside of the visible spectrum.

In other CRI tuned embodiments, the output converted light produced by blending of the constituent converted light of the constituent phosphor compositions combined with radiation produced by the at least one light emitting die that bleeds through the phosphor layer72to contribute to light output of the light emitting package8is white light or substantially white light, that is, lies on or substantially on the black body locus of the 1931 CIE chromaticity diagram. In some such embodiments, the phosphor compositions have color points corresponding to yellowish or orangish light and are suitably operated in conjunction with one or more blue light emitting chips or dice, that is, with chips or dice that emit peak radiation in the blue or bluish visible range. The bleed-through blue or bluish light combines with the yellowish or orangish converted light to provide white light output of the light emitting package. In other such embodiments, the phosphor compositions produce white or substantially white light with low intensity in the blue or bluish range, and the one or more light emitting chips or dice emit peak radiation in the blue or bluish visible range that bolsters the spectrum of the blended light in the blue or bluish range of the visible spectrum.

With reference toFIG. 8, another lighting package8″ includes a printed circuit board10″, having a long strip shape, on which a plurality of light emitting dice or chips12″ are arranged in reflective wells22″ in a double-row arrangement along the board strip. The printed circuit board10″ includes one or more printed circuitry layers30″ sandwiched between insulative layers32″,34″, and a ground plate or metal core38″. Electrical terminals46″ disposed on the printed circuit board10″ deliver electrical power to the light emitting dice or chips12″ via the printed circuitry30″. A light transmissive cover60″ is tube-shaped to cover the long double-row of light emitting dice or chips12″ and has an open end defining a perimeter62″ that is received by a matching groove66″ formed in the printed circuit board10″. The tube-shaped cover60″ together secured to the printed circuit board10″ define an elongated or tubular interior volume70″ containing the light emitting dice or chips12″. A phosphor72″ optionally coats an inside surface of the tube-shaped cover60″. An encapsulant76″ substantially fills the interior volume70″ to encapsulate and pot the light emitting dice or chips12″ and the optional phosphor72″. In some embodiments, it is contemplated to replace the illustrated electric terminals46″ with conventional fluorescent tube end-terminals, and to include power-conditioning circuitry on the printed circuit board10″ so that the lighting package8″ is suitable for retrofit into a fluorescent lighting fixture.

With reference toFIG. 9, yet another lighting package208includes a printed circuit board210on which one or more (specifically three in the illustrated embodiment) light emitting dice or chips212are arranged. In the lighting package208, the light emitting dice or chips212are not disposed in reflective wells; rather, they are surface-mounted to a level surface of the printed circuit board210. The printed circuit board210includes one or more printed circuitry layers230sandwiched between insulative layers232,234, and a ground plate or metal core238. A zener diode component244provides electrostatic discharge protection for the light emitting dice or chips212. Electrical terminals246disposed on the printed circuit board210deliver electrical power to the light emitting dice or chips212via the printed circuitry230. A light transmissive cover260covers the light emitting dice or chips212and has an open end defining a perimeter262that is connected with the printed circuit board210to define an interior volume270containing the light emitting dice or chips212. A phosphor272optionally coats an inside surface of the light transmissive cover260. The above-described elements of the lighting component or package208are similar to corresponding elements of the lighting component or package8shown inFIGS. 1-3.

The lighting package208differs from the lighting package8in the configuration of the encapsulant disposed in the interior volume. In the lighting package208, a first encapsulant276encapsulates and optionally pots the light emitting dice or chips212, but does not substantially fill the interior volume270. In some embodiments, the first encapsulant276may encapsulate only the one or more light emitting dice212. A second encapsulant278encapsulates the phosphor272if such a phosphor is included in the package208. In some embodiments, the second encapsulant278is the binding material of the phosphor270. For example, the phosphor272may be applied to the inside surface of the cover260, and the encapsulant in this embodiment is the binding material of the applied phosphor. Generally, the first and second encapsulants276,278can be different materials. A substantial gap280extends between the first and second encapsulants276,278. Typically, the gap280contains air; however, it is also contemplated to fill the gap280with an inert gas to reduce moisture in the lighting package208. In yet another embodiment, the gap280is filled with a third encapsulant different from at least one of the first and second encapsulants276,278. In the lighting package208, there is no groove in the printed circuit board210for receiving the perimeter262of the cover260. However, such a groove similar to the groove66of the lighting package8can optionally be provided to align and optionally help secure the cover260to the printed circuit board210.

With continuing reference toFIG. 9and with further reference toFIG. 10, an example process300for manufacturing the lighting package208is described. The light emitting dice or chips212are mechanically and electrically connected with the printed circuit board210in a die attach process302. The die attach can involve flip chip bonding, soldering, wire bonding, or so forth. The attached light emitting dice212are encapsulated or potted on the printed circuit board210in a first encapsulation process304, and the first encapsulant276is cured in a first curing process306applied to the printed circuit board210.

Separately, the inside surface (and/or optionally the outside surface) of the light transmissive cover260is coated with the phosphor272in a phosphorizing process310. In embodiments in which the cover has the phosphor embedded therein, the phosphorizing process310is omitted and instead the phosphor is incorporated during molding or other formation of the cover260. The phosphor is encapsulated on the light transmissive cover260in a second encapsulation process312, and the second encapsulant278is cured in a second curing process314applied to the light transmissive cover314. If the phosphor272is omitted from the package208, then process310,312, and314are suitably omitted. In some embodiments the second encapsulant278is the binding material of the phosphor272; in these embodiments, the phosphorization process310and the second encapsulation process312are integrated. The light transmissive cover is then secured, optionally sealed, to the printed circuit board210in a securing process316. The securing process316defines the interior volume270, which is optionally a hermetically sealed volume.

With reference toFIG. 11, still yet another lighting package408includes a printed circuit board410on which a single light emitting die or chip412is surface-mounted to a level surface of the printed circuit board410. The printed circuit board410includes two printed circuit traces430,431disposed on the same surface as the light emitting die412. The two conductive traces430,431can be formed by metal evaporation or the like. Wire bonds436,437connect top-side electrodes of the light emitting die or chip412with the conductive traces430,431. The printed circuit board includes an insulative layer432on which the two printed circuit traces430,431are formed, and an optional ground plate or metal core438. A light transmissive cover460covers the light emitting die or chip412and has an open end defining a perimeter462that is connected with the printed circuit board410to define an interior volume470containing the light emitting die or chip412. The two printed circuit traces430,431extend from inside the cover460to outside the cover460to provide electrical communication into the interior volume470. A phosphor472optionally coats an inside surface of the light transmissive cover460, and an encapsulant476substantially fills the interior volume470. Hemispherical openings480,482formed at the perimeter462of the light transmissive cover460allow for injection of the encapsulant material and corresponding displacement of air. That is, the openings480,482of the lighting package408serve the same purpose as the printed circuit board openings80,82of the lighting package8(seeFIG. 3).

With continuing reference toFIG. 11, a reflective coating488coats the inside surface of the light transmissive cover. The reflective coating488is substantially reflective for light produced by the light emitting die or chip412but is substantially transmissive for light produced by the phosphor472responsive to illumination by the light emitting die or chip412. In the lighting package408, the phosphor472is disposed on the reflective coating488and extends some distance into the encapsulant476.

With reference toFIG. 12, another example embodiment lighting package508is shown. A common printed circuit board510supports a plurality of light transmissive dome-shaped covers560each covering one or more light emitting dice512. Printed circuitry of the common printed circuit board510connects the light emitting dice512with edge terminals446,447that are adapted for connection with a DIN-type rail lighting fixture. In other contemplated embodiments, other types of terminals are employed. For example, the electric terminals46shown inFIG. 1can be used.

In some contemplated embodiments, the printed circuit board510is a flexible printed circuit board, so that the light source ofFIG. 12is a flexible sheet lighting source. In such flexible embodiments the light emitting covers560provide mechanical protection for the light emitting dice512. In some embodiments, the perimeter of each light transmissive dome-shaped cover560is secured to the flexible printed circuit board in a manner so as to impart tensile strain to the portion of the flexible circuit board covered by the dome-shaped cover560. In this way, the portions of the flexible printed circuit board on which the light emitting dice512are disposed are kept substantially rigid by the tensile strain as the flexible printed circuit board is flexed, thus reducing a likelihood that the flexing will break the connections or bonds of the light emitting dice512with the printed circuit board. In some embodiments, the light transmissive dome-shaped covers560are arranged close together such that, together with light-dispersive properties of the covers560, optional dispersive particles disposed in an encapsulant within the covers560, light spreading provided by the distribution of phosphor across the covers560, or so forth, a spatially uniform planar lighting source508is formed that produces little or no perceptible pixilation of the illumination at typical illumination source-to-target distances.

One advantage of the lighting packaging techniques disclosed herein is flexibility in deployment of phosphor compositions. One or more phosphor layers are readily disposed on the inner surface of the cover, for example as described previously with respect to phosphorization operations104,310ofFIGS. 4 and 10, respectively. Application of a layer of phosphor to a glass or plastic cover surface can be done in a precise and readily controllable manner. Each phosphor layer suitably includes a phosphor composition comprising one or more phosphor compounds.

With reference toFIGS. 13 and 14, a lighting package608includes a printed circuit board610supporting a light emitting die or chip612, or optionally more than one light emitting die or chip, covered by a light transmissive cover660. Thus, the lighting package608is similar to the lighting package8ofFIGS. 1-3. However, the lighting package608includes two phosphor layers LA, LBof different phosphor compositions disposed on an inner surface of the light-transmissive dome-shaped cover660. The phosphor composition of phosphor layer LBis different from the phosphor composition of layer LAin that they include at least one different phosphor compound. The lighting package608optionally includes other features set forth herein with respect to other embodiments, such as an optional ultraviolet reflective coating688diagrammatically shown inFIG. 14disposed between the cover660and the phosphor layers LA, LB. The ultraviolet reflective coating688is useful for embodiments in which the light emitting die or chip612emits ultraviolet light while the phosphor layers LA, LBgenerate visible light.

While two phosphor layers LA, LBare illustrated, it will be appreciated that three or more phosphor layers can be provided so as to produce light output which is a blend three or more phosphors. The dome-shaped cover660provides a convenient platform for arranging one, two, or more phosphor layers each of which emits a spatially uniform distribution of light subtending about 2π steradians or more.

It is contemplated to employ the layered approach ofFIGS. 13 and 14in conjunction with the tunable CRI concept discussed previously. For example, the first phosphor layer LAmay include a first constituent phosphor composition of blue, green, and yellow phosphor compounds A, B, and C, respectively, with a stoichiometry producing white or substantially white light at a first CRI value, while the second phosphor layer LBmay include a second constituent phosphor composition of green, yellow, and red phosphor compounds B, C, and D, respectively, with a stoichiometry producing white or substantially white light at a second, different CRI value. The layered combination of the first constituent phosphor composition of layer LAand the second constituent phosphor composition of layer LBproduces a CRI value that is different from, and possibly larger than, the first or second CRI value.

CRI tuning using a single layer containing two or more constituent phosphor compositions of about the same color point has been described with example reference toFIG. 3. CRI tuning using a layered structure in which each layer contains one of the constituent phosphor compositions of about the same color point has been described with example reference toFIGS. 13 and 14. The two or more constituent phosphor compositions whose light is blended to produce a tailored CRI and/or luminosity can be combined in other physical arrangements, such as being disposed as distinct patterns in a single layer.

With continuing reference toFIGS. 13 and 14, in some cases one of the phosphor compositions may become saturated at high levels of irradiation intensity by the light emitting die or chip612. The layered arrangement ofFIGS. 13 and 14can also be useful in addressing such saturation issues. The more easily saturated phosphor composition is suitably arranged as the phosphor layer LAthat is furthest from the light emitting die or chip612, since partial absorption of light by the intervening phosphor composition of phosphor layer LBcan be expected to reduce the excitation light flux of the phosphor composition in layer LA, thus facilitating more efficient light conversion.

It is to be appreciated that the phosphors can be disposed in other spatially separated arrangements besides layers. For example, in some embodiments, the first phosphor composition may be arranged physically as a layer disposed on an inside or outside surface of the light-transmissive cover, while the second phosphor composition may be dispersed in an encapsulant filling the interior volume.

With reference toFIG. 15, a light-transmissive cover having other than a dome-shaped geometry can be employed.FIG. 15shows a lighting package708that includes a printed circuit board710supporting a light emitting die or chip712, or optionally more than one light emitting die or chip, covered by a light transmissive cover760. Thus, the lighting package708is similar to the lighting package608ofFIGS. 13 and 14, except that the light-transmissive cover760has a different geometry than the dome-shaped cover660ofFIGS. 13 and 14. The light-transmissive cover760includes a reflective side portion or portions760Rthat channel light (indicated diagrammatically inFIG. 15by two drawn rays) toward a light-transmissive top portion760T. Two phosphor layers LX, LYof different phosphor compositions (that is, having at least one different phosphor compound) are disposed on the light-transmissive top portion760T. Optionally, the two phosphor layers LX, LYmay also extend along the inside of the reflective side portion760Rof the light-transmissive cover760. In some contemplated embodiments, the phosphor layers are disposed only on the inside reflective side portion760Rof the light-transmissive cover760, while the light-transmissive top portion760Tis left uncoated by phosphor. In those of such embodiments that employ an ultraviolet-emitting die or chip712, the light-transmissive top portion760Tis preferably absorbing or reflective for ultraviolet light to prevent direct ultraviolet light from being emitted from the lighting package708.

With reference toFIG. 16, depending upon how the phosphor layer or layers are disposed on the light-transmissive cover, a logo, picture, symbol, pattern, or other depiction can be generated.FIG. 16shows a perspective view of another lighting component or package similar to that ofFIGS. 1-3, but having two different phosphor compositions disposed on different regions800,802screen-printed on the light-transmissive dome-shaped cover60. The screen-printed phosphor region800spells out “Acme Corp.” along with a corresponding logo, while the screen-printed phosphor region802covers the area of the light-transmissive dome-shaped cover60not covered by the phosphor regions800. If, for example, the phosphor composition of the region800emits red light while the phosphor composition of the region802emits white light, then when the one or more light emitting dice or chips within the cover60are energized, the name “Acme Corp.” and corresponding logo appears in as a red light-emissive text and symbol on a white light emissive background. Advantageously, when using two different phosphor compounds in respective regions to define the logo, picture, symbol, pattern, or other depiction, both the foreground (e.g., text or logo artwork) and the background are light-emissive.

The appended claims follow: