WO2020033327A1

WO2020033327A1 - Inert filler to increase wavelength converting material volume and improve color over angle

Info

Publication number: WO2020033327A1
Application number: PCT/US2019/045148
Authority: WO
Inventors: Rene Helbing; Daniel ESTRADA; Kentaro Shimizu
Original assignee: Lumileds Llc
Priority date: 2018-08-06
Filing date: 2019-08-05
Publication date: 2020-02-13

Abstract

Devices and techniques are disclosed herein which include a die (321) including side surfaces such that light emitted from the die (321) can exit through the side surfaces. The die includes a first surface and a second surface opposite the first surface such that the distance between the first surface and the second surface is at least 100 micro meters. The die also includes a wavelength converting material (340) deposited external to the die (321) such that the wavelength converting material (340) covers the side surfaces. The wavelength converting material (340) includes phosphor particles, a transparent resin carrier, and transparent particles (350) configured to increase the volume of the wavelength converting material, the transparent particles (350) having a refractive index (Rl) that is similar to the Rl of the transparent resin carrier.

Description

INERT FILLER TO INCREASE WAVELENGTH CONVERTING MATERIAL VOLUME AND IMPROVE COLOR OVER ANGLE

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit of priority to U.S. Patent Application No. 16/055,965 filed August 6, 2018 and to European Patent Application No 18201255.9 filed October 12, 2018, each of which is incorporated herein by reference in its entirety.

BACKGROUND

[0002] Light emitting diodes (LEDs) are commonly used as light sources in various applications. LEDs can be more energy-efficient than traditional light sources, providing much higher energy conversion efficiency than incandescent lamps and fluorescent light, for example.

[0003] Increasing the height of an LED die can improve light extraction efficiency from the LED, because the surface area of the side surfaces of a taller die is greater in comparison to the surface area of the side surfaces of similar shorter die, allowing more light to escape through the side surfaces of the taller die.

SUMMARY

[0004] According to aspects of the disclosure, a device is disclosed which include a die including side surfaces such that light emitted from the die can exit through the side surfaces. The die includes a first surface and a second surface opposite the first surface such that the distance between the first surface and the second surface is at least 100 micro meters. The die also include a wavelength converting material deposited external to the die such that the wavelength converting material covers the side surfaces. The wavelength converting material includes phosphor particles, a transparent resin carrier, and transparent particles configured to increase the volume of the wavelength converting material, the transparent particles having a refractive index (RI) that is similar to the RI of the transparent resin carrier.

[0005] According to aspects of the disclosure, a method for producing a LED die is disclosed. The method includes manufacturing a wavelength converting material including phosphor particles, a transparent resin, and transparent particles configured to increase the volume of the wavelength converting material, the transparent particles having a refractive index (RI) that is similar to the RI of the transparent resin carrier. The manufactured wavelength converting material may be deposited over an LED die that is at least 100 micro meters in height, such that the manufactured wavelength converting material covers the sides of the LED. The manufactured wavelength converting material may experience sedimentation such that phosphor particles in the manufactured wavelength converting material covers the sides of the LED die after such sedimentation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The drawings described below are for illustration purposes only, and are not intended to limit the scope of the present disclosure. Like reference characters shown in the figures designate like parts in the various embodiments.

[0007] FIG. 1 A is a diagram of an example light emitting device that that includes a light emitting semiconductor diode structure and a wavelength converting structure.

[0008] FIG. 1B is a diagram of an example light emitting semiconductor diode structure that may be included in the light emitting device of FIG. 1 A.

[0009] FIG. 2 is a diagram of another example light emitting device that device that that includes a light emitting semiconductor diode structure and a wavelength converting structure.

[0010] FIG. 3 A is a diagram of an example of a light emitting device that includes a light emitting semiconductor diode structure and a wavelength converting structure, in which phosphor particles in the wavelength converting structure have sedimented to below the height of the LED and do not fully and uniformly cover the sides of the LED.

[0011] FIG. 3B is a diagram of an example of a light emitting device that includes a light emitting semiconductor diode structure and a wavelength converting structure, in which transparent filler particles in the wavelength converting structure prevent phosphor particles from sedimenting below the height of the LED. The phosphor particles cover the sides of the LED substantially uniformly.

[0012] FIG. 4A is a graph representing the distribution of color over angle for a light emitting device as in Fig. 3 A.

[0013] FIG. 4B is a graph representing the distribution of color over angle for a light emitting device as in Fig. 3B.

[0014] FIG. 5 is a flowchart outlining a process for making a light emitting device as in Figure 3B and obtaining a distribution of color over angle as shown in Fig. 4B.

DETAILED DESCRIPTION

[0015] According to aspects of the disclosure, to improve light extraction efficiency, taller LED dies can be used in light emitting devices. The taller dies may result in improved light output due to the increased surface area made available at the sides of a die as a result of the die being taller. For example, a die that is 100 micro meters tall will have a smaller side surface area in comparison with a die that is, for example, 200 micro meters tall but otherwise of the same shape and dimensions.

[0016] A conventional wavelength converting material comprising phosphor particles dispersed in a binder (e.g., a silicone) may be deposited on LED dies to convert the light (e.g., blue light) emitted from the die to a different color. The phosphor particles may for example absorb blue light emitted by the LED die and in response emit yellow, green, and/or red light. The output from the device may be a mix of light emitted by the LED die and light emitted by the phosphor particles, and may for example appear white.

[0017] During deposition of such a wavelength converting material, the phosphor particles typically settle (sediment) through the binder material to a lower level. Such a conventional wavelength converting material may effectively cover the top surface as well as the side surfaces of a short LED die (e.g., a 100 micro meter tall die), but might not effectively cover the side surfaces of a taller die because the phosphor particles sediment to below the top surface of the die. Accordingly, at least a portion of the light from the taller die may escape via the side surfaces of the die without encountering phosphor particles. (See, e.g., FIG. 3B and related discussion below).

[0018] If some or all of the light escaping through sides of the LED does not encounter and interact with the phosphor particles, there may result an undesirable increase in a deviation in color over angle (COA). That is, the color of light emitted by the light emitting device can vary as a result of the angle by which light exits the LED die, if the phosphor particles in the wavelength converting material are not distributed on the sides and top of the LED die substantially uniformly. At certain angles more of the blue light will be absorbed and converted to other wavelengths by phosphor particles, compared to other angles.

Accordingly, an LED may emit different colors which are visible at different angles from the LED. Such differences in colors emitted over different angles are not desirable, especially in an LED being used to emit a single color.

[0019] As disclosed herein, a wavelength converting material may comprise a

homogenous mixture of phosphor particles and inert transparent filler particles dispersed in a binder. The transparent filler particles increase the volume of the wavelength converting material, for the same amount of phosphor particles. As explained in more detail below with respect to Figure 3B, such a wavelength converting material may provide improved coverage of the sides of a tall LED die, and thus improve color over angle for the light output from the light emitting device, compared to conventional wavelength converting materials. This occurs because the presence of the transparent filler particles prevents the phosphor particles from settling or sedimenting to as low a level as they would in the absence of the filler particles.

[0020] The transparent filler particles may be silica particles, for example, and may be selected to be inert in the sense that they do not significantly affect the optical properties of the device by scattering, absorbing, or emitting light.

[0021] Examples of different light emitting devices will be described more fully hereinafter with reference to the accompanying drawings. These examples are not mutually exclusive, and features found in one example can be combined with features found in one or more other examples to achieve additional implementations. Accordingly, it will be understood that the examples shown in the accompanying drawings are provided for illustrative purposes only and they are not intended to limit the disclosure in any way. Like numbers refer to like elements throughout.

[0022] It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

[0023] It will be understood that when an element such as a layer, region or substrate is referred to as being "on" or extending "onto" another element, it can be directly on or extend directly onto the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" or extending "directly onto" another element, there are no intervening elements present. It will also be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present. It will be understood that these terms are intended to encompass different orientations of the element in addition to any orientation depicted in the figures. [0024] Relative terms such as "below" or "above" or "upper" or "lower" or "horizontal" or "vertical" may be used herein to describe a relationship of one element, layer or region to another element, layer or region as illustrated in the figures. It will be understood that these terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures.

[0025] FIG. 1 A is a diagram of an example light emitting element device 100 that includes a light emitting semiconductor diode structure 115, a wavelength converting structure 110, and an optional coating 105 on the wavelength converting material 110.

Although FIG. 1 A shows wavelength converting structure 110 covering only the top surface of light emitting semiconductor diode structure 115, as explained above in the light emitting devices disclosed herein the wavelength converting structure extends to cover the side surfaces as well. Contacts 120 and 125 may be coupled to the light emitting semiconductor structure 115, either directly or via another structure such as a submount, for electrical connection to a circuit board or other substrate or device. In embodiments, the contacts 120 and 125 may be electrically insulated from one another by a gap 127, which may be filled with a dielectric material. The light emitting semiconductor diode structure 115 may be any light emitting semiconductor diode structure that emits light that may be converted to light having a different color point via a wavelength converting material. For example, the light emitting semiconductor structure 115 may be formed from III-V semiconductors including, but not limited to, A1N, A1P, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, II- VI semiconductors including, but not limited to, ZnS, ZnSe, CdSe, CdTe, group IV semiconductors including, but not limited to Ge, Si, SiC, and mixtures or alloys thereof.

These example semiconductors have indices of refraction ranging from about 2.4 to about 4.1 at the typical emission wavelengths of LEDs in which they are present. For example, Ill- Nitride semiconductors, such as GaN, have refractive indices of about 2.4 at 500 nm, and III- Phosphide semiconductors, such as InGaP, have refractive indices of about 3.7 at 600 nm. Contacts 120 and 125 may be formed from a solder, such as AuSn, AuGa, AuSi or SAC solders.

[0026] FIG. 1B is a diagram of an example light emitting semiconductor structure 115 that may be included in the light emitting device 100 of FIG. 1A. The illustrated example is a flip chip structure. However, one of ordinary skill in the art will understand that the embodiments described herein may be applied to other types of LED designs, such as vertical, lateral, and multi -junction devices. [0027] In the example illustrated in FIG. 1B, the light emitting semiconductor diode structure 115 includes a light emitting active region 135 disposed between a semiconductor layer or semiconductor region of n-type conductivity (also referred to as an n-type region)

130 and a semiconductor layer or region of p-type conductivity (also referred to as a p-type region) 140. Contacts 145 and 150 are disposed in contact with a surface of the light emitting semiconductor structure 115 and electrically insulated from one another by a gap 155, which may be filled by a dielectric material, such as an oxide or nitride of silicon (i.e., Si02 or Si3N4). In the illustrated embodiment, contact 145 (also referred to as a p-contact) is in direct contact with a surface of the p-type region 140, and the contact 150 (also referred to as an n-contact) is in direct contact with a surface of the n-type region 130. Although not shown in FIG. 1B, a dielectric material, such as disposed in the gap 155, may also line side walls of the light emitting active region 135 and p-type region 140 to electrically insulate those regions from the contact 150 to prevent shorting of the p-n junction.

[0028] The n-type region 130 may be grown on a growth substrate and may include one or more layers of semiconductor material. Such layer or layers may include different compositions and dopant concentrations including, for example, preparation layers, such as buffer or nucleation layers, and/or layers designed to facilitate removal of the growth substrate. These layers may be n-type or not intentionally doped, or may even be p-type device layers. The layers may be designed for particular optical, material, or electrical properties desirable for the light emitting region to efficiently emit light. Like the n-type region 130, the p-type region 140 may include multiple layers of different composition, thickness, and dopant concentrations, including layers that are not intentionally doped, or n- type layers. While layer 130 is described herein as the n-type region and layer 140 is described herein as the p-type region, the n-type and p-type regions could also be switched without departing from the scope of the embodiments described herein.

[0029] The light emitting active region 135 may be, for example, a p-n diode junction associated with the interface of p-region 140 and n-region 135. Alternatively, the light emitting active region 135 may include one or more semiconductor layers that are doped n- type or p-type or are un-doped. For example, the light emitting active region 135 may include a single thick or thin light emitting layer. This includes a homojunction, single

heterostructure, double heterostructure, or single quantum well structure. Alternatively, the light emitting active region 135 may be a multiple quantum well light emitting region, which may include multiple quantum well light emitting layers separated by barrier layers. [0030] The p-contact 145 may be formed on a surface of the p-type region 140. The p- contact 145 may include multiple conductive layers, such as a reflective metal and a guard metal, which may prevent or reduce electromigration of the reflective metal. The reflective metal may be silver or any other suitable material, and the guard metal may be TiW or TiWN. The n-contact 150 may be formed in contact with a surface of the n-type region 130 in an area where portions of the active region 135, the n-type region 140, and the p-contact 145 have been removed to expose at least a portion of the surface of the n-type region 130. The sidewall of the exposed mesa or via may be coated with a dielectric to prevent shorting. The contacts 145 and 150 may be, for example, metal contacts formed from metals including, but not limited to, gold, silver, nickel, aluminum, titanium, chromium, platinum, palladium, rhodium, rhenium, ruthenium, tungsten, and mixtures or alloys thereof. In other examples, one or both contacts 145 and 150 may be formed from transparent conductors, such as indium tin oxide.

[0031] The n-contact 150 and p-contact 145 are not limited to the arrangement illustrated in FIG. 1B and may be arranged in any number of different ways. In embodiments, one or more n-contact vias may be formed in the light emitting semiconductor structure 115 to make electrical contact between the n-contact 150 and the n-type layer 130. Alternatively, the n- contact 150 and p-contact 145 may be redistributed to form bond pads with a dielectric/metal stack as known in the art. The p-contact 145 and the n-contact 150 may be electrically connected to the contacts 120 and 125 of FIG. 1 A, respectively, either directly or via another structure, such as a submount.

[0032] As described above, the wavelength converting material 110 comprises phosphor particles dispersed in a transparent or translucent matrix binder material. As used herein, “phosphor” is intended to refer to any material that may absorb light emitted by the light emitting semiconductor diode structure and in response emit longer wavelength light, such as for example inorganic phosphor materials and semiconductor quantum dots.

[0033] The wavelength converting material 110 may be applied in a layer having a thickness that may depend on the wavelength converting material used or other factors related to providing a desired output from the light emitting device.

[0034] In embodiments, the light emitting semiconductor structure 115 may emit blue light. In such embodiments, the wavelength converting material 110 may include, for example, a yellow emitting wavelength converting material or green and red emitting wavelength converting materials, which will produce white light when the light emitted by the respective phosphors combines with the blue light emitted by the light emitting semiconductor structure 115. In other embodiments, the light emitting semiconductor structure 115 emits UV light. In such embodiments, the wavelength converting material 110 may include, for example, blue and yellow wavelength converting materials or blue, green and red wavelength converting materials. Wavelength converting materials emitting other colors of light may be added to tailor the spectrum of light emitted from the device 100.

[0035] In embodiments, the wavelength converting material 110 may be composed of Y3Al50l2:Ce3+. The wavelength converting material 110 may be an amber to red emitting rare earth metal-activated oxonitridoalumosilicate of the general formula (Cal-x-y- zSrxBayMgz)l-n(All-a+bBa)Sil-bN3-bOb:REn wherein 0<x<l, 0<y<l, 0<z<l, 0<a<l, 0<b<l and 0.002<n<0.2, and RE may be selected from europium(II) and cerium(III). The phosphor may also be an oxido-nitrido-silicate of general formula EA2-zSi5-aBaN8- aOa:Lnz, wherein 0<z<l and 0<a<5, including at least one element EA selected from the group consisting of Mg, Ca, Sr, Ba and Zn and at least one element B selected from the group consisting of Al, Ga and In, and being activated by a lanthanide (Ln) selected from the group consisting of cerium, europium, terbium, praseodymium and mixtures thereof.

[0036] In other embodiments, the wavelength converting material 110 may include aluminum garnet phosphors with the general formula (Lul-x-y-a-bYxGdy)3(All-zGaz)50l2: CeaPrb, wherein 0<x<l, 0<y<l, 0<z<0.l, 0<a<0.2 and 0<b<0.l, such as Lu3Al50l2:Ce3+ and Y3Al50l2:Ce3+, which emits light in the yellow-green range; and (Srl-x-yBaxCay)2- zSi5-aAlaN8-aOa:Euz 2+, wherein 0<a<5, 0<x<l, 0<y<l, and 0<z<l such as

Sr2Si5N8:Eu2+, which emits light in the red range. Other green, yellow and red emitting phosphors may also be suitable, including (Srl-a-bCabBac)SixNyOz:Eua 2+; (a=0.002-0.2, b=0.0-0.25, c=0.0-0.25, x=l.5-2.5, y=l.5-2.5, z=l.5-2.5) including, SrSi2N202:Eu2+; (Srl- u-v-xMguCavBax)(Ga2-y-zAlyInzS4):Eu2+ including, for example, SrGa2S4:Eu2+; Srl- xBaxSi04:Eu2+; and (Cal-xSrx)S:Eu2+ wherein 0<x<l including, CaS:Eu2+ and SrS:Eu2+. Other suitable phosphors include, CaAlSiN3:Eu2+,(Sr,Ca)AlSiN3:Eu2+, and (Sr, Ca, Mg,

Ba, Zn)(Al, B, In, Ga)(Si, Ge)N3:Eu2+.

[0037] In other embodiments, the wavelength conversion material 110 may also have a general formula (Srl-a-bCabBacMgdZne)SixNyOz:Eua 2+, wherein 0.002<a<0.2,

0.0<b<0.25, 0.0<c<0.25, 0.0<d<0.25, 0.0<e<0.25, l.5<x<2.5, l.5<y<2.5 andl.5<z<2.5. The wavelength conversion material may also have a general formula of MmAaBbOoNmZz where an element M is one or more bivalent elements, an element A is one or more trivalent elements, an element B is one or more tetravalent elements, O is oxygen that is optional and may not be in the phosphor plate, N is nitrogen, an element Z that is an activator,

n=2/3m+a+4/3b-2/3o, wherein m, a, b can all be 1 and o can be 0 and n can be 3. M is one or more elements selected from Mg (magnesium), Ca (calcium), Sr (strontium), Ba (barium) and Zn (zinc), the element A is one or more elements selected from B (boron), Al (aluminum), In (indium) and Ga (gallium), the element B is Si (silicon) and/or Ge (germanium), and the element Z is one or more elements selected from rare earth or transition metals. The element Z is at ]east one or more elements selected from Eu (europium), Mg (manganese), Sm (samarium) and Ce (cerium). The element A can be Al (aluminum), the element B can be Si (silicon), and the element Z can be Eu (europium).

[0038] The wavelength conversion material 110 may also be an Eu2+ activated Sr— SiON having the formula (Srl-a-bCabBac)SixNyOx:Eua, wherein a=0.002-0.2, b=0.0-0.25, c=0.0-0.25, x=l.5-2.5, y=l.5-2.5.

[0039] The wavelength conversion material 110 may also be a chemically-altered Ce: YAG (Yttrium Aluminum Garnet) phosphor that is produced by doping the Ce: YAG phosphor with the trivalent ion of praseodymium (Pr). The wavelength conversion material 110 may include a main fluorescent material and a supplemental fluorescent material. The main fluorescent material may be a Ce: YAG phosphor and the supplementary fluorescent material may be europium (Eu) activated strontium sulfide (SrS) phosphor (“Eu:SrS”). The main fluorescence material may also be a Ce: YAG phosphor or any other suitable yellow- emitting phosphor, and the supplementary fluorescent material may also be a mixed ternary crystalline material of calcium sulfide (CaS) and strontium sulfide (SrS) activated with europium ((CaxSrl_ x)S:Eu2+). The main fluorescent material may also be a Ce:YAG phosphor or any other suitable yellow-emitting phosphor, and the supplementary fluorescent material may also be a nitrido-silicate doped with europium. The nitrido-silicate

supplementary fluorescent material may have the chemical formula (Srl-x-y- zBaxCay)2Si5N8:Euz 2+ where 0<x, y<0.5 and 0<z<0.l.

[0040] In embodiments, the wavelength conversion material 110 may include strontium- lithium-aluminum: europium (II) ion (SrLiAl3 N4:Eu2+) class (also referred to as SLA), including MLiAl3N4: Eu2+ (M = Sr, Ba, Ca, Mg). In a specific embodiment, the

luminescent particles may be selected from the following group of luminescent material systems: MLiAl3N4:Eu (M=Sr, Ba, Ca, Mg), M2Si04:Eu (M=Ba, Sr, Ca) , MSel-xSx:Eu (M=Sr, Ca, Mg), MSr2S4:Eu (M=Sr, Ca), M2SiF6:Mn (M=Na, K, Rb), M2TiF6:Mn (M=Na, K, Rb), MSi A1N3 :Eu (M=Ca, Sr), M8Mg(Si04)4Cl2:Eu (M=Ca, Sr), M3MgSi208:Eu (M=Sr, Ba, Ca), MSi202N2:Eu (M=Ba, Sr, Ca), M2Si5-xAlxOxN8-x:Eu (M=Sr, Ca, Ba). However, other systems may also be of interest and may be protected by a coating. Also combinations of particles of two or more different luminescent materials may be applied, such as e.g. a green or a yellow luminescent material in combination with a red luminescent material.

[0041] In embodiments, the wavelength conversion material 110 may be a blend of any of the above-described phosphors.

[0042] FIG. 2 is a diagram of an example light emitting device 200A that includes the light emitting semiconductor structure 115 of FIG. 1B mounted to a submount 205 that includes contacts 120 and 125. The light emitting semiconductor structure 115 may be mounted to the submount 205 by an electrical coupling between the contacts 145 and 150 on the light emitting semiconductor diode structure 115 and submount electrodes on an adjacent surface of the submount 205 (not shown in FIG. 2). The submount electrodes may be electrically connected by vias (not shown) to the contacts 120 and 125 on the opposite surface of the submount 205. In embodiments, the light emitting device 200 A may be mounted to a printed circuit board (PCB) 215. In such embodiments, the submount 205 may be mounted via the contacts 120 and 125 to the PCB 215. Metal traces on the circuit board may electrically couple the contacts 120 and 125 to a power supply, such that an operational or drive voltage and current may be applied to the LED when it is desired to turn the LED on.

[0043] The submount 205 may be formed from any suitable material, such as ceramic, Si, or aluminum. If the submount material is conductive, an insulating material may be disposed over the substrate material, and the metal electrode pattern may be formed over the insulating material. The submount 205 may act as a mechanical support, provide an electrical interface between the n and p electrodes on the LED chip and a power supply, and provide heat sinking. In embodiments, a heat sink may alternatively or additionally be provided on the PCB 215, such as a metal core PCB-MCPCB heat sink 220 illustrated in FIG. 2. While the heat sink 220 is illustrated in FIG. 2 as being attached to the bottom of the PCB 215, one of ordinary skill in the art will recognize that other arrangements are possible without departing from the scope of the embodiments described herein.

[0044] In the example illustrated in Figure 2, the wavelength converting material 110 completely surrounds the light emitting semiconductor structure 115 on all surfaces except the surface that electrically connects the light emitting semiconductor structure 115 to the submount 205. The optional coating 105 may be disposed in direct contact with the wavelength converting material 110. The coating may not be a separate layer, and may be a coating on the individual phosphor particles, and this coating may include pores. These pores may be filled with a binder or matrix material and may be part of the wavelength converter 110. Coatings of phosphor materials are described in U.S. Patent Appln. No. 15/802, 273, which was filed on November 2, 2017 and is incorporated by reference herein in its entirety. Phosphor coatings of sol-gel, atomic layer deposition (ALD), evaporation, sputtering, dip and dry, or spin coating methods include Si02, A1203, Hf02, Ta205, Zr02, Ti02, Y203, and Nb205. Coatings may be thick enough to include pores that may be formed during or after deposition.

[0045] As explained above, the wavelength converting structure 110 includes transparent filler particles. The transparent particles may be any suitable transparent particles based on the disclosure herein and may, for example, be silica, glass, fluorides such as calcium fluoride, sulfates, plastics, or the like. The transparent particles cause the volume of the wavelength converting material to be greater than the volume of the wavelength converting material without the transparent particles. Notably, the transparent particles cause the volume of the wavelength converting material to be large enough such that the phosphor particles in the wavelength converting material cover the side surfaces of the die.

[0046] Fig. 3 A shows an example semiconductor LED 300 with a substrate 310 and LED die 320. The LED die 320 may be a semiconductor device made of any applicable material such as, but not limited to III-V semiconductors including, but not limited to, A1N, A1P,

AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, II- VI semiconductors including, but not limited to, ZnS, ZnSe, CdSe, CdTe, group IV semiconductors including, but not limited to Ge, Si, SiC, and mixtures or alloys thereof. When electric current passes through the die, it may emit a light such as, for example, a blue light. One or more die may be mounted to a substrate 310 which may be made of aluminum, ceramic, other applicable materials or combinations thereof. The die 320 may be a tall die such that its height may be greater than or equal to 100 or 150 micro meters. According to an implementation, the die 320 may be a tall die such that its height may be greater than or equal to 200 micro meters. According to an implementation, the die 320 may be a tall die such that its height may be greater than or equal to 250 micro meters.

[0047] Fig. 3A shows a conventional wavelength converting material 330 disposed on and around top and sides surfaces of die 320. Wavelength converting material 330 does not include transparent particles. As, a result the phosphor particles in wavelength converting material 330 cover only a portion of the side surfaces of the die 320 such that a portion 331 of the die is exposed. That is, the phosphor particles settled to well below a top surface of die

320 as a result of sedimentation.

[0048] At least a portion of the light emitted from the die 320 may exit the die through region 331 without passing through or interacting with phosphor particles in wavelength converting material 330. As a result, as disclosed herein, the COA for the light emitted by the semiconductor LED 300 may be undesirably high.

[0049] Fig. 4A shows a graph 400 which shows the COA 410 of the LED device of Fig. 3 A. The horizontal axis corresponds to the angle of view from the LED device such that 0 corresponds to a perpendicular view of the LED device and 90/-90 correspond to a parallel view of the LED device. The vertical axis corresponds to a color value deviation du V where a color value deviation of 0, viewed from a perpendicular position that is directly above the LED device 300 of Fig. 3 A may be an ideal color value. As shown, the COA deviates from 0 to approximately .012 (or 12 points), as shown in Fig. 4A for the device 300 of Fig. 3A. A deviation of .012 (or 12 points) may be considered a large deviation and may not be desirable. According to an implementation a du V of .08 (or 8 points) may be preferred.

The wavelength converting material 330 may include wavelength converting elements and a binder (carrier) to hold the wavelength converting materials together. The carrier may be a transparent resin carrier such as a silicone carrier

[0050] Fig. 3B shows an example semiconductor LED 301 with substrate 311 and LED die 321. The LED die 321 may be a semiconductor device made any applicable material such as, but not limited to III-V semiconductors including, but not limited to, A1N, A1P, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, II- VI semiconductors including, but not limited to, ZnS, ZnSe, CdSe, CdTe, group IV semiconductors including, but not limited to Ge, Si, SiC, and mixtures or alloys thereof. When electric current passes through the die, it may emit a light such as, for example, a blue light. One or more die may be mounted to a substrate 311 which may be made of aluminum or ceramic or combinations thereof. The die

321 may be a tall die such that its height may be greater than or equal to 100 or 150 micro meters. According to an implementation, the die 321 may be a tall die such that its height may be greater than or equal to 200 micro meters. According to an implementation, the die 321 may be a tall die such that its height may be greater than or equal to 250 micro meters. [0051] Fig. 3B shows a wavelength converting material 340 including transparent particles (e.g., silica particles) 350 in addition to phosphor particles and binder material (e.g., silicone). The wavelength conversion material may also include a stabilizing agent that helps to maintain a homogeneous distribution of the phosphor particles and the transparent particles in the wavelength conversion material. The use of such a stabilizing agent may enable the wavelength converting material to be more thixotropic.

[0052] As shown in Fig. 3B, the transparent particles 350 may increase the volume of the wavelength converting material 340 such that phosphor particles in the wavelength converting material 340 cover the side walls of the die 321 after sedimentation has occurred. According to an implementation, at least 50% of a side of a die may be covered by wavelength converting material with transparent particles, as disclosed herein, after the sedimentation process. As a result, all or substantially all of the light emitted by the die 321 may pass through or interact with phosphor particles in the wavelength converting material 340. The COA of the light emitted from by the die 321 may therefore be lower than that of the light emitted by the die 320 of Fig. 3 A.

[0053] Fig. 4B shows a graph 401 which shows the COA 420 of the LED device of Fig. 3B. The horizontal axis corresponds to the angle of view from the LED device such that 0 corresponds to a perpendicular view of the LED device and 90/-90 correspond to a parallel view of the LED device. The vertical axis corresponds to a color value deviation where a color value deviation of 0, viewed from a perpendicular position that is directly above the LED device 301 of Fig. 3B may be an ideal color value. As shown, the COA deviates from 0 to approximately .003, as shown in Fig. 4B for the device 301 of Fig. 3B. A deviation of .003 may be considered an acceptable deviation. As a comparison, Fig. 4A, as described herein, shows the COA 410 of device 300 of Fig. 3A where the wavelength converting material 330 does not cover the sides of the die 320. As a result, the color deviation of up to .012, as shown in Fig. 4A, is experienced for the device 300 of Fig. 3A.

[0054] Further, it should be noted that simply increasing the amount of wavelength converting material used in order to cover the sides of a semiconductor’s die may not be a viable option as such an increase may prohibitively increase the cost of manufacturing.

Additionally, increasing the amount of wavelength converting material may also change the color point of the wavelength converting material, which may not be desirable.

Consequently, use of transparent filler particles described herein may be advantageous [0055] The transparent particles 350 may be, for example, fused quartz or fused silica and may be glass consisting of silica in amorphous (non-crystalline) form. The silica may be manufactured, configured or otherwise have properties such that the optical properties of a die and/or wavelength converting material are not altered.

[0056] The transparent particles may be transparent such that no or minimal absorption of light occurs at the transparent particles. The particle size of the transparent particles may be similar to the particle size of the wavelength converting material. For example, if the wavelength converting material includes phosphor, then the phosphor particle size may be similar to the transparent particle size. Such particles may range from 5 micro meters to 50 micro meters. Additionally, the transparent particles may have properties such that the transparent particles do not affect silicone curing.

[0057] Notably, the transparent particles may have a refractive index (RI) that is substantially similar to the RI of the transparent resin carrier in the wavelength converting material. The RI indicates the amount that a light, which passes through a material, bends.

The transparent particles having an RI that is substantially similar to the RI of the transparent resin carrier (e.g., a silicone carrier) of the wavelength converting material may allow a light to propagate a wavelength converting material with transparent particles as it would propagate the wavelength converting material if without transparent particles. According to an implementation, the RI of the transparent particles may be within 5% of the RI of a wavelength converting material transparent resin carrier. According to another

implementation, the RI of the transparent particles may be within 2% of the RI of the wavelength converting material transparent resin carrier.

[0058] According to implementations disclosed herein, the semiconductor LED devices, such as the semiconductor LED devices 300 and 301 of Figs. 3A and 3B, respectively, may be chip on board (COB) devices. COB devices may be bonded directly to a substrate to form a single module. Such devices may use a single circuit and multiple devices may share electrical contacts.

[0059] According to implementations disclosed herein, the semiconductor LED devices, such as the semiconductor LED devices 300 and 301 of Figs. 3A and 3B, respectively, may be part of a wafer which contains multiple devices and which may be singulated to produce individual dies.

[0060] Flowchart 500 of Fig. 5 shows a technique for manufacturing or producing an LED die based on the techniques disclosed herein. As shown at step 510, a wavelength converting material may be manufactured and may include phosphor particles, a silicone carrier, and transparent particles (e.g., silica particles) as disclosed herein. The transparent particles may be configured to increase the volume of the wavelength converting material and may have a refractive index (RI) that is similar to the RI of the transparent resin carrier.

[0061] At step 520 of Fig. 5, the manufactured wavelength converting material may be deposited over an LED die that is at least 100 micro meters in height. The wavelength converting material may cover the side surfaces of the LED die. At step 530, the wavelength converting material may sediment. The wavelength converting material may cover the side surfaces of the LED even after the sedemntation.

[0062] The figures provided herein are provided as an example only. At least some of the elements discussed with respect to these figures can be arranged in different order, combined, and/or altogether omitted. It will be understood that the provision of the examples described herein, as well as clauses phrased as“such as,”“e.g.”,“including”,“in some aspects,”“in some implementations,” and the like should not be interpreted as limiting the disclosed subject matter to the specific examples.

[0063] Having described the invention in detail, those skilled in the art will appreciate that, given the present disclosure, modifications may be made to the invention without departing from the spirit of the inventive concepts described herein. Therefore, it is not intended that the scope of the invention be limited to the specific embodiments illustrated and described.

Claims

CLAIMS What is claimed is:

1. A light emitting device comprising:

a semiconductor light emitting diode die comprising a light emitting first surface and a second surface located opposite from the first surface at a distance of at least 100 microns from the first surface, and light emitting side surfaces connecting the light emitting first surface and the second surface; and

a wavelength converting material disposed on the light emitting first surface and the light emitting side surfaces of the die, the wavelength converting material comprising phosphor particles and transparent particles dispersed in a transparent resin material, the transparent particles having a refractive index approximately matching a refractive index of the binder material, and phosphor particles in the wavelength material distributed uniformly on the sides of the die from the second surface to at least 50% of the distance between the second surface and the first surface.

2. The light emitting device of claim 1, wherein phosphor particles in the wavelength material are distributed uniformly along the sides of the die from the second surface to at least 75% of the distance between the second surface and the first surface.

3. The light emitting device of claim 2, wherein phosphor particles in the wavelength material are distributed uniformly along the sides of the die along the full length of the distance between the second surface and the first surface.

4. The light emitting device of claim 1, wherein the refractive index of the transparent particles and the refractive index of the resin differ by 5% or less.

5. The light emitting device of claim 4, wherein the refractive index of the transparent particles and the refractive index of the resin differ by 2% or less.

6. The light emitting device of claim 1, wherein the wavelength converting material comprises a stabilizer promoting a homogenous distribution of the phosphor particles and transparent particles in the resin.

7. The device of claim 1, wherein a color over angle (COA) variation is less than 8 points du V .

8. The light emitting device of any of claims 1-7, wherein the second surface is locate at least 150 microns from the first surface.

9. The light emitting device of any of claims 1-7, wherein the second surface is located at least 200 microns from the first surface.

10. The light emitting device of any of claims 1-7, wherein the second surface is located at least 250 microns from the first surface.

11. A method comprising:

disposing a wavelength converting material comprising phosphor particles and transparent particles in a resin on a light emitting first surface and light emitting sides surfaces of a semiconductor light emitting diode die, the light emitting first surface oppositely positioned form a second surface of the semiconductor light emitting diode die located at least 100 microns from the first surface, the light emitting side surfaces connecting the light emitting first surface and the second surface; and

sedimenting the phosphor particles and the transparent resin particles to form a uniform distribution of phosphor particles on the sides of the die from the second surface to at least 50% of the distance between the second surface and the first surface.

12. The light emitting device of claim 11, comprising sedimenting the phosphor particles and the transparent resin particles to form a uniform distribution of phosphor particles on the sides of the die from the second surface to at least 75% of the distance between the second surface and the first surface.

13. The light emitting device of claim 11, comprising sedimenting the phosphor particles and the transparent resin particles to form a uniform distribution of phosphor particles on the sides of the die along the full length of the distance between the second surface and the first surface.

14. The light emitting device of claim 11, wherein the refractive index of the transparent particles and the refractive index of the resin differ by 5% or less.

15. The light emitting device of claim 11 wherein the refractive index of the transparent particles and the refractive index of the resin differ by 2% or less.

16. The light emitting device of claim 11, wherein the wavelength converting material comprises a stabilizer promoting a homogenous distribution of the phosphor particles and transparent particles in the resin.

17. The device of claim 11, wherein a color over angle (COA) variation is less than 8 points du V .

18. The light emitting device of any of claims 11-17, wherein the second surface is locate at least 150 microns from the first surface.

19. The light emitting device of any of claims 11-17, wherein the second surface is located at least 200 microns from the first surface.

20. The light emitting device of any of claims 11-17, wherein the second surface is located at least 250 microns from the first surface.