Encapsulation structures for light-emitting diode packages

Abstract

This invention discloses a light-emitting diode (LED) device, and more particularly, an encapsulation structure in an LED package. The encapsulation structure comprises an encapsulation having a host material and diffuse particles disposed within the host material. Different diffuse particles can be configured to provide different optical properties, including increased reflection, increased refraction, and / or altered mechanical properties of the host material. Some diffuse particles are preferably configured to form along weaknesses in the encapsulation material, such as along the corners between the recessed base plate and the recessed sidewalls of the LED package, to provide increased heat absorption in localized areas during thermal cycling. An LED display having an LED package comprising such an encapsulation structure is also disclosed.

Description

[Technical Field]

[0001] This invention relates to light-emitting diode (LED) devices, and more particularly to encapsulation structures in LED packages. [Previous Technology]

[0002] Solid-state light-emitting devices, such as light-emitting diodes (LEDs), are increasingly used in both consumer and commercial applications. Advances in LED technology have resulted in highly efficient and mechanically robust light sources with long lifespans. As a result, modern LEDs have enabled a variety of new display applications and are increasingly used in general lighting applications, often replacing incandescent and fluorescent light sources.

[0003] A light-emitting diode (LED) is a solid-state device that converts electrical energy into light, and typically includes one or more active layers (or active regions) of semiconductor material disposed between oppositely doped n-type and p-type layers. When a bias voltage is applied across the doped layers, holes and electrons are injected into one or more active layers, where the holes and electrons recombine to produce emission, such as visible light or ultraviolet light emission. An LED chip typically includes active regions that may be made of, for example, gallium nitride, gallium phosphide, aluminum nitride, indium nitride, gallium indium phosphate, gallium arsenide, and / or organic semiconductor materials.

[0004] LED packages have evolved to provide mechanical support, electrical connections, and encapsulation for LED emitters. Light-emitting materials, such as phosphors, can also be arranged close to the LED emitter to convert the emitted light into different wavelengths. As LED technology continues to evolve for increasingly sophisticated modern applications, challenges remain in maintaining the operational requirements of LED packages and related components. In some applications, LED packages are used for displays based on LEDs in outdoor applications and / or other locations exposed to adverse environmental conditions.

[0005] This technology continues to seek improved light-emitting diodes and solid-state light-emitting devices with the required lighting characteristics that can overcome the challenges associated with conventional light-emitting devices. [Summary of the Invention]

[0006] This invention relates to light-emitting diode devices, and more particularly to encapsulation structures in LED packages. The encapsulation structure includes an encapsulation element having a host material and diffuse particles disposed within the host material. Different diffuse particles can be configured to provide different optical properties, including increased reflection, increased refraction, and / or altered mechanical properties of the host material. Some diffuse particles are preferably configured to form along weaknesses in the encapsulation material, such as along the corners between the recessed base plate and the recessed sidewalls of the LED package, to provide increased heat absorption in localized areas during thermal cycling. An LED display having an LED package including such an encapsulation structure is also disclosed.

[0007] In one embodiment, the LED package includes: a light-emitting diode (LED) package comprising: a support structure forming a recess with a recessed base plate; one or more LED chips located at the recessed base plate; and an encapsulation member within the recess and above the one or more LED chips, the encapsulation member comprising: a body material; a first plurality of diffuse particles within the body material; a second plurality of diffuse particles within the body material; and a third plurality of diffuse particles within the body material, the third plurality of diffuse particles being arranged at the recessed base plate at a concentration higher than that of the first plurality of diffuse particles or the second plurality of diffuse particles. In some embodiments, the third plurality of diffuse particles are arranged at the recessed base plate at a concentration higher than the combined concentration of the first plurality of diffuse particles and the second plurality of diffuse particles. In some embodiments: the recess further forms one or more recess sidewalls and one or more recess corners, the one or more recess corners being at the junction between the recess base plate and the recess sidewalls; and a third plurality of diffuse particles are arranged at one or more recess corners at a concentration higher than that of the first plurality of diffuse particles or the second plurality of diffuse particles.

[0008] In some embodiments: the encapsulation forms a first sub-region and a second sub-region, the first sub-region being along a recessed base plate and one or more recessed corners, such that the first sub-region is between the second sub-region and the recessed base plate; a third plurality of diffuse particles are arranged in the first sub-region at a concentration higher than that of the first plurality of diffuse particles or the second plurality of diffuse particles; and a third plurality of diffuse particles are arranged in the second sub-region at a concentration lower than that of one or more of the first plurality of diffuse particles and the second plurality of diffuse particles. In some embodiments, the first sub-region is a first encapsulation layer and the second sub-region is a second encapsulation layer. In some embodiments, the first sub-region is further arranged along the top surface of one or more LED chips. The LED package may further include a wire bond connected to the top surface of one or more LED chips, wherein the first sub-region is further arranged along the wire bond.

[0009] In some embodiments, the support structure includes a lead frame structure having a housing, and a recess is formed within the housing. In some embodiments: the recess further forms one or more recess sidewalls and one or more recess corners, the one or more recess corners being at the junction between the recess base plate and the recess sidewalls; and portions of one or more leads of the lead frame structure extend from within the housing and pass through portions of the one or more recess corners.

[0010] In some embodiments, the main material includes epoxy resin. In some embodiments, the third plurality of diffuse particles includes fused silica. In some embodiments: the first plurality of diffuse particles includes a first surface morphology; the second plurality of diffuse particles includes a second surface morphology different from the first surface morphology; and the third plurality of diffuse particles includes a third surface morphology different from both the first and second surface morphologies. In some embodiments, the third surface morphology is spherical and non-porous. In some embodiments, the first surface morphology is non-porous, and the second surface morphology is porous. In some embodiments: the first plurality of diffuse particles includes a first median particle size distribution ranging from 7µm to 13µm; the second plurality of diffuse particles includes a second median particle size distribution ranging from 4µm to 5µm; and the third plurality of diffuse particles includes a third median particle size distribution ranging from 4µm to 6µm.

[0011] In other embodiments, the LED display includes: a display panel; and at least one LED package, comprising: a support structure forming a recess with a recessed base plate; one or more LED chips located at the recessed base plate; and an encapsulation within the recess and above the one or more LED chips, the encapsulation comprising: a body material; a first plurality of diffuse particles within the body material; a second plurality of diffuse particles within the body material; and a third plurality of diffuse particles within the body material, the third plurality of diffuse particles being arranged at the recessed base plate at a concentration higher than that of the first plurality of diffuse particles or the second plurality of diffuse particles. In some embodiments, the third plurality of diffuse particles are arranged at the recessed base plate at a concentration higher than the combined concentration of the first plurality of diffuse particles and the second plurality of diffuse particles. In some embodiments: the recess further forms one or more recess sidewalls and one or more recess corners at the junction between the recess base plate and the recess sidewalls; and a third plurality of diffuse particles are arranged at the one or more recess corners at a concentration higher than that of the first plurality of diffuse particles or the second plurality of diffuse particles. In some embodiments: the encapsulation forms a first sub-region and a second sub-region, the first sub-region being along the recess base plate and one or more recess corners, such that the first sub-region is between the second sub-region and the recess base plate; a third plurality of diffuse particles are arranged in the first sub-region at a concentration higher than that of the first plurality of diffuse particles or the second plurality of diffuse particles; and a third plurality of diffuse particles are arranged in the second sub-region at a concentration lower than that of one or more of the first plurality of diffuse particles and the second plurality of diffuse particles. In some embodiments, the support structure includes a lead frame structure having a shell, and the recess is formed within the shell. In some embodiments: the first plurality of diffuse particles include a first surface morphology; the second plurality of diffuse particles include a second surface morphology different from the first surface morphology; and the third plurality of diffuse particles include a third surface morphology different from both the first and second surface morphologies. In some embodiments: the first plurality of diffuse particles include a first median particle size distribution ranging from 7µm to 13µm; the second plurality of diffuse particles include a second median particle size distribution ranging from 4µm to 5µm; and the third plurality of diffuse particles include a third median particle size distribution ranging from 4µm to 6µm.

[0012] In another configuration, any of the aforementioned configurations and / or various independent configurations and features described herein may be combined individually or together to obtain additional advantages. Unless otherwise indicated herein, any of the various features and elements disclosed herein may be combined with one or more of the other features and elements disclosed.

[0013] Those skilled in the art will understand the scope of the invention and will recognize additional features of the invention after reading the following detailed description of preferred embodiments in conjunction with the accompanying drawings.

Implementation Method

[0025] The embodiments described below illustrate the information necessary for those skilled in the art to practice the embodiments, and depict the best mode of practicing the embodiments. Those skilled in the art will understand the concept of the invention and recognize the application of the concepts not specifically stated herein after reading the following illustrations in conjunction with the accompanying drawings. It should be understood that the concepts and applications described are within the scope of the present invention and the appended patent applications.

[0026] It should be understood that although the terms first, second, etc., may be used herein to describe various elements, the elements should not be limited by the terms. The terms are used only to distinguish one element from another. For example, a first element may be referred to as a second element without departing from the scope of the invention, and similarly, a second element may be referred to as a first element. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0027] It should be understood that when an element such as a layer, region, or substrate is referred to as being "on" or extending "on" another element, it may be directly on or directly extending to the other element, or an intervening element may also be present. In contrast, when an element is referred to as "directly located on" or "directly extending to" another element, no intervening element is present. Similarly, it should be understood that when an element such as a layer, region, or substrate is referred to as "located above" or "extending above" another element, it may be directly above or directly extending above the other element, or an intervening element may also be present. In contrast, when an element is referred to as "directly located above" or "directly extending above" another element, no intervening element is present. It should also be understood that when an element is referred to as "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or an intervening element may be present. In contrast, when an element is referred to as "directly connected" or "directly coupled" to another element, no intervening element is present.

[0028] Relative terms such as “below” or “above”, or “upper” or “lower”, or “horizontal” or “vertical” may be used herein to describe the relationship between one element, layer or region and another element, layer or region as illustrated in the figures. It should be understood that the terms mentioned above, as well as the terms discussed above, are intended to cover different device orientations other than those depicted in the figures.

[0029] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, unless the context clearly indicates otherwise, the singular forms "a" and "the" are intended to include the plural forms as well. It should be further understood that the terms "comprising" and / or "including" as used herein specify the presence of the stated features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof.

[0030] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should be further understood that the terms used herein should be interpreted as having the meaning appropriate to their context in this specification and in the relevant art, and should not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0031] Embodiments are described herein with reference to illustrative drawings of embodiments of the invention. Therefore, the actual dimensions of layers and elements may differ, and variations in the shape of the drawings are anticipated due to, for example, manufacturing techniques and / or tolerances. For instance, areas illustrated or described as squares or rectangles may have circular or curved features, and areas shown as straight lines may have some irregularity. Therefore, the areas illustrated in the figures are illustrative, and their shapes are not intended to depict the precise shape of areas of the device, nor are they intended to limit the scope of the invention. Furthermore, for illustrative purposes, the dimensions of structures or areas may be enlarged relative to other structures or areas, and thus, the general structure provided to illustrate the subject matter of the invention may or may not be drawn to scale. Common elements between the figures may be shown herein with common element symbols and may not be described again subsequently.

[0032] This invention relates to light-emitting diode devices, and more particularly to encapsulation structures in LED packages. The encapsulation structure includes an encapsulation element having a host material and diffuse particles disposed within the host material. Different diffuse particles can be configured to provide different optical properties, including increased reflection, increased refraction, and / or altered mechanical properties of the host material. Some diffuse particles are preferably configured to be formed along weaknesses in the encapsulation material, such as along the corner between the recessed base plate and the recessed sidewall of the LED package, to provide increased heat absorption for localized areas during thermal cycling. An LED display having an LED package including such an encapsulation structure is also disclosed.

[0033] Before delving into the specific details of the various embodiments of the present invention, an overview of various elements that may be included in the exemplary light-emitting diode package of the present invention is provided to provide context. Light-emitting diode wafers typically include active light-emitting diode structures or regions, which may have many different semiconductor layers arranged in different ways. The fabrication and operation of light-emitting diodes and their active structures are generally known in the art and are only briefly discussed herein. The layers of the active light-emitting diode structure can be fabricated using known processes, with metal-organic chemical vapor deposition being a suitable process. The layers of the active light-emitting diode structure may include many different layers and typically include an active layer sandwiched between n-type and p-type oppositely doped epitaxial layers, both continuously formed on a growth substrate. It should be understood that additional layers and elements may also be included in the active light-emitting diode structure, including (but not limited to) buffer layers, nucleation layers, superlattice structures, undoped layers, cladding layers, contact layers, and current-dispersing layers and light-extracting layers and elements. The active layer may include single quantum wells, multiple quantum wells, dual heterostructures, or superlattice structures.

[0034] Active light-emitting diode (LED) structures can be fabricated from different material systems, some of which are based on group III nitrides. Group III nitrides refer to semiconductor compounds formed between nitrogen (N) and elements in group III of the periodic table, typically aluminum (LED), gallium (Ga), and indium (In). Gallium nitride (GaN) is a common binary compound. Group III nitrides also refer to ternary and quaternary compounds, such as aluminum gallium nitride (AlGaN), indium gallium nitride (InGaN), and aluminum indium gallium nitride (AlInGaN). For group III nitrides, silicon (Si) is typically an n-type dopant and magnesium (Mg) is typically a p-type dopant. Therefore, the active layer, n-type layer, and p-type layer can comprise one or more layers of undoped or doped GaN, AlGaN, InGaN, and AlInGaN based on Si or Mg in a group III nitride material system. Other material systems include organic semiconductor materials and other group III to V systems and related compounds such as gallium phosphide (GaP), gallium arsenide (GaAs), etc. The active light-emitting diode structure can be grown on a growth substrate, which can contain many materials such as sapphire, SiC, Si, aluminum nitride (AlN), and GaN.

[0035] Different embodiments of the active-emitting diode (AEB) structure may emit light of different wavelengths depending on the composition of the active layer. In some embodiments, the AEB structure may emit blue light with a peak wavelength range of approximately 430 nanometers (nm) to 480 nm. In other embodiments, the AEB structure emits green light with a peak wavelength range of 500 nm to 570 nm. In other embodiments, the AEB structure emits red light with a peak wavelength range of 600 nm to 700 nm. In some embodiments, the AEB structure may be configured to emit light beyond the visible spectrum, including one or more portions of the ultraviolet (UV) spectrum, or one or more portions of the near-infrared spectrum, and / or the infrared spectrum (e.g., 700 nm to 1000 nm). The UV spectrum is typically divided into three wavelength range categories denoted by the letters A, B, and C. In this way, UV-A light is typically defined as having a peak wavelength in the range of 315 nm to 400 nm, UV-B as having a peak wavelength in the range of 280 nm to 315 nm, and UV-C as having a peak wavelength in the range of 100 nm to 280 nm. UV light-emitting diodes (LEDs) are particularly suitable for applications related to the disinfection of microorganisms in air, water, and surfaces, as well as other applications. In other applications, UV LEDs can also incorporate one or more luminescent materials to provide the LED package with dense emission that offers a broad spectrum and improved color quality for visible light applications.

[0036] The present invention can be applied to multi-chip LED packages, wherein the multi-chip LEDs are arranged within a common recess and sometimes below a common lens of the LED package. In some embodiments, the LED package may include red, green, and blue LED chips to position the LED package as pixels in an LED display. In other embodiments, the present invention can be applied to other LED packages, such as those comprising one or more LED chips having a recipient lumiphoric material that converts at least a portion of the light generated by the one or more LED chips into different wavelengths.

[0037] The light-emitting diode (LED) chip may also be covered by one or more luminescent materials, such as phosphors (also referred to herein as luminescent materials), such that at least some of the light from the LED chip is absorbed by one or more luminescent materials and emitted according to the characteristics of the one or more luminescent materials, thus being converted into one or more different wavelength spectra. In this respect, at least one luminescent material receiving at least a portion of the light generated by the LED source may re-emit light having a different peak wavelength than that of the LED source. The LED source and one or more luminescent materials may be selected such that their combined output produces light having one or more desired characteristics, such as color, color point intensity, etc. In some embodiments, the emission of the aggregated LED chip may optionally be combined with one or more luminescent materials and may be arranged to provide cool white, natural white, or warm white light, such as in a color temperature range from 2500 Kelvin (K) to 10,000 K. In some embodiments, luminescent materials having cyan, green, amber, yellow, orange, and / or red peak emission wavelengths may be used. In some embodiments, the combination of a light-emitting diode chip and one or more light-emitting elements (e.g., phosphors) emits a general white light combination. The one or more phosphors may comprise yellow (e.g., YAG:Ce), green (e.g., LuAg:Ce), and red (e.g., Cai-x-ySrxEuyAlSiN3), which emit phosphorescence and combinations thereof.

[0038] The luminescent material described herein may be or comprise one or more phosphors, scintillators, lumiphoric inks, quantum dot materials, day glow tape, and the like. The luminescent material may be provided by any suitable means, for example, dispersed in an encapsulating material disposed to cover one or more LEDs and directly coated (plated) onto one or more surfaces of the LEDs, and / or coated (plated) onto one or more optical or support elements (e.g., by powder coating, inkjet printing, or the like). In some embodiments, the luminescent material may be down-converted or up-converted, and may be provided as a combination of both down-converted and up-converted materials. In some embodiments, multiple different (e.g., different compositions) luminescent materials are arranged to produce different peak wavelengths, which may be arranged to receive emission from one or more LED chips. One or more luminescent materials may be provided in various configurations on one or more portions of the LED chip. In some embodiments, the luminescent material may be provided above one or more surfaces of the LED chip, while other surfaces of the LED chip may not have the luminescent material.

[0039] As used herein, a layer or region is considered "transparent" when at least 80% of the emitted radiation impacting a layer or region of the light-emitting device passes through it. Furthermore, as used herein, a layer or region of an LED is considered "reflective," or embodies a "mirror" or "reflector," when at least 80% of the emitted radiation impacting a layer or region is reflected. In some embodiments, the emitted radiation includes visible light from LEDs such as blue and / or green LEDs, with or without a light-emitting material. In other embodiments, the emitted radiation may include invisible light. For example, in the context of GaN-based blue and / or green LEDs, silver (Ag) can be considered a reflective material (e.g., with a reflectivity of at least 80%).

[0040] This invention is useful for LED chips with geometric variations, such as vertical geometry or lateral geometry. A vertical geometry LED chip typically includes anode and cathode connections on opposite sides or faces of the LED chip. A lateral geometry LED chip typically includes both anode and cathode connections on the same side of the LED chip opposite a substrate, such as a growth substrate. In some embodiments, the lateral geometry LED chip may be mounted on a sub-substrate of an LED package such that the anode and cathode connections are located on the face of the LED chip opposite the sub-substrate. In this configuration, wire bonding may be used to provide electrical connections to the anode and cathode connections. In other embodiments, the lateral geometry LED chip may be flip-chip mounted on the surface of a sub-substrate of an LED package such that the anode and cathode connections are located on the face of the active LED structure adjacent to the sub-substrate. In this configuration, traces or patterns may be provided on the sub-substrate to provide electrical connections to the anode and cathode connections of the LED chip. In the flip-chip configuration, the active LED structure is disposed between the substrate of the LED chip and the sub-substrate for the LED package. Thus, light emitted from the active LED structure can pass through the substrate in the desired emission direction. In other embodiments, the active LED structure may be bonded to a carrier sub-substrate, and the growth substrate may be removed so that light can exit the active LED structure without passing through the growth substrate.

[0041] According to an embodiment of the present invention, an LED package may include one or more elements provided together with one or more LED chips, such as light-emitting materials, encapsulation, light-modifying materials, lenses, and electrical contacts, and other elements. In some embodiments, the LED package may include support members, such as a sub-substrate or lead frame. Suitable materials for the sub-substrate include, but are not limited to, ceramic materials, such as alumina or bauxite, AlN, or organic insulators, such as polyimide (PI) and polyphthalamide (PPA). In other embodiments, the sub-substrate may include a printed circuit board (PCB), sapphire, Si, or any other suitable material. For PCB embodiments, different PCB types may be used, such as standard FR-4 PCB, metal-core PCB, or any other type of PCB. In yet another embodiment, the support structure may embody a lead frame structure. Light-modifying materials may be disposed within the LED package to reflect or otherwise redirect light from one or more LED chips in a desired emission direction or pattern.

[0042] In some embodiments, the present invention relates to an LED package in which the lead frame structure is at least partially enclosed by a body or housing. The lead frame structure may typically be formed of a metal such as copper, a copper alloy, or other conductive metal. The lead frame structure may initially be part of a larger metal structure that is unified during the manufacture of an individual LED package. Within an individual LED package, the insulating portion of the lead frame structure may form anode and cathode connections for the LED chip. The body or housing may be formed of an insulating material arranged to surround or enclose portions of the lead frame structure. For example, the body or housing may comprise one or more of PPA, PCT, EMC, FR4, BT, impregnated fibers, and / or plastics. Before unification, a housing may be formed on the lead frame structure such that individual lead frame portions are electrically isolated from each other and mechanically supported by the housing within the individual LED package. The housing may form a cup or recess, wherein one or more LED chips may be mounted to the lead frame at the base of the recess. Part of the lead frame structure may extend from the recess and through the housing to protrude or reach the outside of the housing to provide external electrical connection. Encapsulation materials such as polysiloxane, epoxy resin, or polymethyl methacrylate (PMMA), or other encapsulation materials, may fill the recess to encapsulate one or more LED chips. In some embodiments, one or more light-emitting materials, such as phosphor particles, may be integrated or otherwise embedded within the encapsulation material.

[0043] In conventional LED packages, the adhesive between the encapsulating material and the sidewalls of the recess can be damaged by heat and / or physical stress during operation, particularly for LED packages used in outdoor environments. In some cases, encapsulation delamination can occur along the sidewalls of the recess, thereby allowing moisture intrusion paths into the LED package. In LED packages with leadframe structures, additional moisture intrusion paths can form at the interface between the leadframe and the housing. Conventional encapsulations used in LED packages may require a trade-off between moisture intrusion protection and package integrity. For example, conventional encapsulating materials with a high degree of moisture intrusion resistance often come with a trade-off of increased rigidity that can contribute to damage to the LED chip and / or bonding. LED packages are subject to thermal cycling during use and the associated thermal stresses that may include rigid encapsulating materials, especially at any weak points. Other conventional encapsulating materials with less rigidity may be more susceptible to moisture intrusion and long-term reliability issues.

[0044] According to an embodiment of the invention, the encapsulation structure is described as providing improved robustness against moisture intrusion and increased stability during thermal cycling. The encapsulation structure comprises an encapsulation having a host material and an arrangement of diffuse particles within the host material. Exemplary host materials comprise various epoxy resins with or without additives, such as aliphatic epoxy resins, amines, polyesters, phenolic aliphatic compounds, and anhydride derivatives. Various diffuse particles can provide increased opacity for LED encapsulations and provide a matte effect, which is beneficial for providing increased contrast in LED display applications. Different diffuse particles can be configured to provide different optical properties, including increased reflection, increased refraction, and / or altered mechanical properties of the host material. In some embodiments, various diffuse particles can be configured to synergistically modify and / or enhance optical properties and / or the overall encapsulation system's properties in conjunction with other different diffuse particles. As used herein, diffuse particles are not referred to as light-emitting particles such as phosphors, which convert the received light wavelength to other wavelengths.

[0045] Exemplary diffuse particles may comprise silica (SiO2) and / or fused silica, titanium oxide comprising titanium dioxide (TiO2), bauxite such as alumina (Al2O3), and combinations thereof. In some embodiments, the encapsulation may comprise three different types of diffuse particles, each having a different surface morphology. Different surface morphologies may include angular and non-porous particles, porous particles, and spherical particles. Angular and non-porous particles can provide increased reflective properties, porous particles can provide increased refractive properties, and spherical particles can promote increased settling along the package substrate to reduce rigidity at weak points in conventional packages. In some embodiments, such encapsulation structures are well-suited for use in LED packages with housings comprising polyimides (e.g., nylon) such as polyphthalamides (PPA), polyesters such as polycyclohexylenedimethylene terephthalate (PCT), epoxy-molding compounds (EMC), and silicone. The housing material may further comprise pigments such as TiO2, composite fibers, or fillers such as SiO2 or talc, as well as other additives for various property modifications.

[0046] FIG1A is a top view of the LED package 10. The LED package 10 includes a lead frame structure formed by a plurality of leads 12-1 to 12-6, a body or housing 14 enclosing a portion of the lead frame structure, and a capsule 16 disposed within a recess 14R formed by the housing 14. FIG1B is a cross-sectional view of the LED package 10 of FIG1A taken along the cross-section 1B-1B of FIG1A. The LED package 10 includes LED chips 18-1 to 18-3, which are respectively mounted on and electrically coupled to leads 12-1 to 12-3, and electrically coupled to corresponding leads 12-4 to 12-6 by means of wire bonding 20. Although each LED chip 18-1 to 18-3 is shown with only a single wire bond 20, it should be understood that each of the LED chips 18-1 to 18-3 may embody a lateral structure, where a second wire bond may be used to provide electrical coupling.

[0047] In some configurations, each of the LED chips 18-1 to 18-3 may be configured to emit a wavelength different from that of the other LED chips. For example, LED chip 18-1 may be configured to emit red light, LED chip 18-2 may be configured to emit green light, and LED chip 18-3 may be configured to emit blue light. Although three LED chips 18-1 to 18-3 are illustrated, the principles disclosed herein apply to any number of LED chips within the LED package 10. The recess 14R may include a recess base plate 14F and one or more recess sidewalls 14S. Leads 12-1 to 12-6 may be arranged to extend through the housing 14, and a portion of the leads 12-1 to 12-6 may be arranged along the recess base plate 14F or otherwise exposed at the recess base plate 14F.

[0048] As best illustrated in FIG. 1B, leads 12-2, 12-5 form several bends within the housing 14, thereby providing increased distance for any unwanted moisture intrusion. Although only leads 12-2, 12-5 are visible in the cross-section of FIG. 1B, it should be understood that all leads 12-1 to 12-6 can be formed in the same or similar shapes. Leads 12-2, 12-5 are accessible along the recessed bottom plate 14F for electrical connection with LED chips 18-1 to 18-3. For this purpose, portions of leads 12-1 to 12-6 are located at the junction between the recessed sidewall 14S and the recessed bottom plate 14F, or at the recessed corner 14C. The recessed corner 14C may also correspond to a weakness in the encapsulation 16, particularly for rigid encapsulation materials typically used to prevent moisture intrusion. As described above, thermal stress during operation can weaken the encapsulation 16 at the recessed corner 14C, contributing to reduced sealing. Therefore, harsh environmental conditions can lead to moisture intrusion into the recess 14R as leads 12-1 to 12-6 enter.

[0049] As described above, embodiments of the present invention include an encapsulation having a body material and an arrangement of diffuse particles within the body material. The body material and the arrangement of the diffuse particles are configured to provide resistance to increased moisture intrusion, while also providing localized absorption of thermal expansion caused by thermal cycling. Figures 2 to 4 provide exemplary illustrations of various diffuse particles with different surface morphologies according to the principles of the present invention.

[0050] Figure 2 is an illustration of an encapsulation 16 of a first diffuse particle 22 having an angular and non-porous surface morphology according to the present invention. The first diffuse particle 22 may be embodied in a ground material, such as silica or glass, titanium oxide, bauxite, and combinations thereof. In some embodiments, the first diffuse particle 22 may have a particle size distribution in the range of 7µm to 13µm. In some embodiments, measured by laser diffraction, the first diffuse particle 22 has a median particle size distribution (D50) in the range of 5µm to 15µm or about 10µm, a 10% particle size distribution (D10) value of about 2µm, a 90% particle size distribution (D90) value of about 30µm, and a 99% particle size distribution (D99) value of about 45µm. With scanning electron microscopy (SEM), the complete measurement range may include as low as 1µm to as high as 80µm. In some embodiments, the particle size distribution throughout the first diffuse particles 22 may be broad, asymmetrical, and favor larger particle sizes. With relatively larger particle sizes, the first diffuse particles 22 may have a larger surface area that promotes increased reflectivity, thereby providing improved surface reflection and increased opacity and matte effect compared to the encapsulation in the LED package. As illustrated, the first diffuse particles 22 may be mixed and / or suspended within a host material 24 of one or more various epoxy resin materials as described above. After mixing, the first diffuse particles 22 may remain suspended in situ during the curing of the host material 24.

[0051] Figure 3 is an illustration of an encapsulation 16 of a second diffuse particle 26 having an agglomerated and porous surface morphology according to the present invention. The second diffuse particle 26 may comprise a material similar to the first diffuse particle 22, such as silica or glass, titanium oxide, bauxite, or combinations thereof. However, the second diffuse particle 26 is configured to have a porous surface that promotes increased light refraction. The increased refractive properties provide increased opacity and a matte effect, thereby improving surface reflection and contrast in a manner complementary to the increased reflective properties of the first diffuse particle 22 in Figure 2. In some embodiments, the particle size distribution of the second diffuse particle 26 may be in the range of 4 µm to 5 µm. In some embodiments, the median particle size distribution (D50) of the second diffuse particles 26, as measured by laser diffraction, can be in the range of 4µm to 5µm or about 4.5µm, with a D10 value of about 2.5µm, a D90 value of about 7µm, and a D99 value of about 10µm. The complete measurement range, as characterized by SEM, can range from as low as 1µm to as high as 6µm. In some embodiments, the particle size distribution of the second diffuse particles 26 has a symmetrical normal or Gaussian shape with a generally close distribution. Similar to FIG. 2, the second diffuse particles 26 can be mixed and / or suspended within the host material 24 and remain suspended in situ during subsequent curing.

[0052] Figure 4 is an illustration of an encapsulation 16 having a spherical surface morphology of a third diffuse particle 28 according to the present invention. The third diffuse particle 28 may comprise a material similar to the first and second diffuse particles 22, 26, such as silica or glass, titanium oxide, bauxite, and combinations thereof. However, the third diffuse particle 28 is configured to have a spherical and generally non-porous shape. In some embodiments, the third diffuse particle 28 may have further surface finishing that affects its interaction with the host material. For this purpose, the third diffuse particle 28 may be configured to settle within the host material 24 faster than the first and second diffuse particles 22, 26 before curing in the host material of the encapsulation. This faster settling can provide an increased concentration of the third diffuse particle 28 in target areas (such as along the recessed bottom plate and corresponding recessed corners). The third diffuse particle 28 may also alter the thermal expansion characteristics of the encapsulation, particularly in localized areas of increased concentration, thereby promoting increased absorption of thermal stress during thermal cycling. In some embodiments, the third diffuse particle 28 has a particle size distribution in the range of 4µm to 6µm. In some embodiments, the median particle size distribution (D50) of the third diffuse particle 28, as measured by laser diffraction, may be in the range of 4µm to 6µm or about 5µm, with a D10 value of about 1.8µm, a D90 value of about 12µm, and a D99 value of about 25µm. The D99 number may include some agglomerates. As characterized by SEM, the complete measurement range may include from as low as 1µm to as high as 12µm. In some embodiments, the particle size distribution of the third diffuse particle 28 may have a bimodal shape that decreases by a percentage at 50%, while also having a symmetrical and generally narrow distribution.

[0053] FIG5A is a cross-sectional view of an LED package 30 similar to the LED package 10 of FIG1A and FIG1B, wherein the embodiment arranges diffuse particles of different concentrations in multiple sub-regions 16-1, 16-2 of the encapsulation 16. FIG5B is an enlarged view of a portion of the LED package 30 as defined by the dashed box 5B in FIG5A. As illustrated, the first sub-region 16-1 of the encapsulation 16 is arranged along the recessed bottom plate 14F and at the recessed corner 14C. The first sub-region 16-1 may contain a third diffuse particle 28 with an increased concentration relative to the first diffuse particle 22 and / or the second diffuse particle 26. As described above, the surface morphology of the third diffuse particle 28 is configured as a spherical and non-porous surface, and the third diffuse particle 28 settles faster in the body material 24 of the encapsulation 16 than the first diffuse particle 22 and / or the second diffuse particle 26. For this purpose, the third diffuse particle 28 is preferably formed along the recessed bottom plate 14F and at the recessed corner 14C to form the first sub-region 16-1. Although some of the first diffuse particles 22 and / or the second diffuse particles 26 may form in the first sub-region 16-1, the concentration of the third diffuse particle 28 is higher than the concentration of the first diffuse particles 22 and / or the second diffuse particles 26. In some embodiments, the concentration of the third diffuse particle 28 is higher than the total concentration of the first diffuse particles 22 and / or the second diffuse particles 26. In yet another embodiment, some of the third diffuse particles 28 may be present in the second sub-region 16-2, but with a lower concentration than the first diffuse particles 22 and / or the second diffuse particles 26.

[0054] In a further embodiment, each or even all portions of all second sub-regions 16-2 may be devoid of the third diffuse particles 28. For example, the first sub-region 16-1 and the second sub-region 16-2 may be independently formed and be different layers of the encapsulation 16. In some embodiments, the first sub-region 16-1 may embody a first encapsulation layer, which is formulated and cured within the recess 14R. Thus, the second sub-region 16-2 may embody a second encapsulation layer, which is formulated and cured on the first encapsulation layer.

[0055] As illustrated in Figures 5A and 5B, the first sub-region 16-1 may be further formed along the top surface 18-2T of the LED wafer 18-2 and / or along the surface of the line bond 20. In other embodiments, the first sub-region 16-1 may be formed along one or more sidewalls 18-2S of the LED wafer 18-2. As described above, the third diffuse particles 28 may alter the thermal expansion characteristics of the encapsulation 16, thereby promoting increased absorption of thermal stress during thermal cycling. Such an arrangement may thus increase the integrity of the encapsulation 16 along one or more of the surfaces of the recessed base plate 14F, the recessed corner 14C, the top surface 18-2T and / or the sidewalls 18-2S and / or the surface of the line bond 20 of the LED wafer 18-2.

[0056] FIG6A is a cross-sectional view of an LED package 32 similar to the LED package 30 of FIG5A, wherein the first and second sub-regions 16-1, 16-2 of the encapsulation 16 in the embodiment may not be clearly defined. FIG6B is an enlarged view of a portion of the LED package 32 as defined by the dashed box 6B in FIG6A. Instead of defining the first sub-regions 16-1 and 16-2 as further defined in FIG5A and FIG5B, the third diffuse particles 28 are formed with a gradient concentration from higher to lower, as indicated by arrow 34 in FIG6A. In some embodiments, the first diffuse particles 22 and the second diffuse particles 26 may be further uniformly mixed throughout a portion of the encapsulation 16. As shown in FIG5A and FIG5B, the concentration of the third diffuse particles 28 for the LED package 32 may still be higher than the concentration of the first diffuse particles 22 and / or the second diffuse particles 26 along the recessed bottom plate 14F and the recessed corner 14C.

[0057] As described above, the encapsulation 16 can be distributed into the recess 14R by mixing the first, second, and third diffuse particles 22, 26, and 28 within the bulk material 24, and then formed by curing. In some embodiments, the time elapsed between mixing and curing can be shortened, such that the first, second, and third diffuse particles 22, 26, and 28 are generally more thoroughly mixed than the LED package 30 in Figures 5A and 5B. However, the better settling of the third diffuse particles 28 still provides an increased concentration of the third diffuse particles 28 relative to the first and second diffuse particles 22, 26 along the recess base plate 14F and recess corner 14C. In some embodiments, the concentration of the third diffuse particles 28 is also higher along the top surface 18-2T and / or sidewalls 18-2S of the LED wafer 18-2 and / or along the surface of the line bond 20. The shortened time between mixing and curing can be intentionally designed to control the distribution of the first, second, and third diffuse particles 22, 26, and 28 within the package 16. In other embodiments, a shortened time may be provided during the normal process. For example, the body material 24 and the first, second, and third diffuse particles 22, 26, and 28 may be mixed in bulk form before being sequentially formulated into an array of LED packages and then cured. In this way, the LED packages 32 of Figures 6A and 6B can embody an LED package whose formulation time from the bulk mixture is later than that of the LED packages 30 of Figures 5A and 5B. Thus, with a longer time between mixing and curing, the settling of the third diffuse particles 28 can be more pronounced than in the LED packages 30 of Figures 5A and 5B. In either case, the higher settling concentration of the third diffuse particles 28 can provide increased thermal stress absorption along conventional weaknesses of the package 16 during thermal cycling, such as those located at or near recessed corners 14C.

[0058] FIG7 is a schematic diagram of a portion of an LED display screen 36, namely, for example, an indoor and / or outdoor screen comprising: generally speaking, a display panel comprising a driver PCB 38 carrying a large number of surface-mount devices (SMDs) 40 arranged in columns and rows, each SMD 40 defining a pixel. SMDs 40 may include LED packages having LED chips 18, and the LED packages having LED chips 18 are the LED packages for LED packages 30 of FIG5A and FIG5B as described above and / or LED packages 32 of FIG6A and FIG6B. SMDs 40 are electrically connected to traces or pads on the PCB 38 to respond to appropriate electrical signals to processing and driver circuitry (not shown). As disclosed above, it should be agreed that although FIG7 depicts the LED chips 18 arranged in a linear configuration, in other embodiments, the LED chips 18 may be arranged in different configurations. By forming an encapsulation structure with the diffuse particle distribution described above, the integrity of the SMD 40 inner encapsulation provides increased resistance to moisture intrusion, while also providing localized absorption of thermal stress during thermal cycling. Thus, the LED display screen 36 exhibits improved reliability, reduced sensitivity to moisture intrusion, and increased operational life.

[0059] It is conceivable that any of the foregoing configurations and / or the various individual configurations and features described herein can be combined to obtain additional advantages. Unless otherwise indicated herein, any of the various embodiments disclosed herein may be combined with one or more other disclosed embodiments.

[0060] Those skilled in the art will recognize improvements and modifications to the preferred embodiments of the present invention. All such improvements and modifications are considered to be within the scope of the concepts disclosed herein and the appended claims. [Simplified Explanation of the Diagram]

[0014] The accompanying drawings, together with the accompanying drawings, form part of this specification illustrating several aspects of the present invention, and together with the description serve to explain the principles of the present invention.

[0015] [Figure 1A] is a top view of a light-emitting diode (LED) package, which includes a lead frame structure formed by a plurality of leads, a body or housing enclosing a portion of the lead frame structure, and a capsule disposed in a recess formed by the housing.

[0016] [Figure 1B] is a cross-sectional view of the LED package of Figure 1A obtained along the section line 1B-1B of Figure 1A.

[0017] [Figure 2] is an illustration of a first diffuse particle encapsulation having an angular and non-porous surface morphology according to the present invention.

[0018] [Figure 3] is an illustration of a capsule containing second diffuse particles having an aggregated and porous surface morphology according to the present invention.

[0019] [Figure 4] is an illustration of a capsule containing a third diffuse particle having a spherical surface morphology according to the present invention.

[0020] [Figure 5A] is a cross-sectional view of an LED package similar to the LED package in Figures 1A and 1B. In this embodiment, diffuse particles of different concentrations are arranged in multiple sub-regions of the package.

[0021] [Figure 5B] is an enlarged view of a portion of the LED package as defined by the dashed box 5B in Figure 5A.

[0022] [Figure 6A] is a cross-sectional view of an LED package similar to the LED package in Figure 5A. The first sub-region and the second sub-region of the package in the embodiment may not be clearly defined.

[0023] [Figure 6B] is an enlarged view of a portion of the LED package as defined by the dashed box 6B in Figure 6A.

[0024] [Figure 7] is a schematic diagram of a portion of an LED display having one or more LED packages in accordance with the principles of the present invention.

Claims

1. A light-emitting diode package, comprising: A supporting structure that forms a recess with a recessed bottom plate; One or more light-emitting diode chips are located at the bottom plate of the recess; and a capsule, which is located within the recess and above the one or more light-emitting diode wafers, the capsule comprising: a body material; A first plurality of diffuse particles within the main body material; a second plurality of diffuse particles within the main body material; and a third plurality of diffuse particles within the main body material, wherein the third plurality of diffuse particles are arranged at the recessed bottom plate at a concentration higher than that of the first plurality of diffuse particles or the second plurality of diffuse particles.

2. The light-emitting diode package of claim 1, wherein the third plurality of diffuse particles are arranged at the recessed bottom plate at a concentration higher than the total concentration of the first plurality of diffuse particles and the second plurality of diffuse particles.

3. The light-emitting diode package as described in claim 1, wherein: The recess further forms one or more recess sidewalls and one or more recess corners, the one or more recess corners being at the junction between the recess bottom plate and the recess sidewalls; and the third plurality of diffuse particles are arranged at the one or more recess corners at a concentration higher than that of the first plurality of diffuse particles or the second plurality of diffuse particles.

4. The light-emitting diode package as described in claim 3, wherein: The capsule seal forms a first sub-region and a second sub-region along the recessed bottom plate and one or more recessed corners, such that the first sub-region is between the second sub-region and the recessed bottom plate; the third plurality of diffuse particles are arranged in the first sub-region at a concentration higher than that of the first plurality of diffuse particles or the second plurality of diffuse particles; and the third plurality of diffuse particles are arranged in the second sub-region at a concentration lower than that of one or more of the first plurality of diffuse particles and the second plurality of diffuse particles.

5. The light-emitting diode package of claim 4, wherein the first sub-region is a first encapsulation layer and the second sub-region is a second encapsulation layer.

6. The light-emitting diode package of claim 4, wherein the first sub-region is further arranged along the top surface of the one or more light-emitting diode wafers.

7. The light-emitting diode package of claim 6, further comprising a wire bond connected to the top surface of the one or more light-emitting diode wafers, wherein the first sub-region is further arranged to be bonded along the wire.

8. The light-emitting diode package of claim 1, wherein the support structure includes a lead frame structure having a housing, and the recess is formed within the housing.

9. The light-emitting diode package as described in claim 8, wherein: The recess further forms one or more recess sidewalls and one or more recess corners, the one or more recess corners being at the junction between the recess base plate and the recess sidewalls; and portions of one or more leads of the lead frame structure extend from the housing and pass through portions of the one or more recess corners.

10. The light-emitting diode package of claim 1, wherein the body material comprises epoxy resin.

11. The light-emitting diode package of claim 1, wherein the third plurality of diffuse particles comprises fused silica.

12. The light-emitting diode package as claimed in claim 1, wherein: The first plurality of diffuse particles includes a first surface type; the second plurality of diffuse particles includes a second surface type different from the first surface type; and the third plurality of diffuse particles includes a third surface type different from both the first surface type and the second surface type.

13. The light-emitting diode package as claimed in claim 12, wherein, The third surface morphology is spherical and non-porous.

14. The light-emitting diode package of claim 13, wherein the first surface type is non-porous and the second surface type is porous.

15. The light-emitting diode package as claimed in claim 1, wherein: The first plurality of diffuse particles comprise a first median particle size distribution ranging from 7µm to 13µm; the second plurality of diffuse particles comprise a second median particle size distribution ranging from 4µm to 5µm; and the third plurality of diffuse particles comprise a third median particle size distribution ranging from 4µm to 6µm.

16. A light-emitting diode display, comprising: Display panel; The package includes at least one light-emitting diode (LED) package comprising: a support structure forming a recess with a recessed base plate; one or more LED wafers located at the recessed base plate; and an encapsulation within the recess and above the one or more LED wafers, the encapsulation comprising: a body material; a first plurality of diffuse particles within the body material; a second plurality of diffuse particles within the body material; and a third plurality of diffuse particles within the body material, the third plurality of diffuse particles being arranged at the recessed base plate at a concentration higher than that of the first plurality of diffuse particles or the second plurality of diffuse particles.

17. The light-emitting diode display of claim 16, wherein the third plurality of diffuse particles are arranged at the recessed base plate at a concentration higher than the total concentration of the first plurality of diffuse particles and the second plurality of diffuse particles.

18. A light-emitting diode display as described in claim 16, wherein: The recess further forms one or more recess sidewalls and one or more recess corners, the one or more recess corners being at the junction between the recess bottom plate and the recess sidewalls; and the third plurality of diffuse particles are arranged at the one or more recess corners at a concentration higher than that of the first plurality of diffuse particles or the second plurality of diffuse particles.

19. A light-emitting diode display as described in claim 18, wherein: The capsule seal forms a first sub-region and a second sub-region along the recessed bottom plate and one or more recessed corners, such that the first sub-region is between the second sub-region and the recessed bottom plate; the third plurality of diffuse particles are arranged in the first sub-region at a concentration higher than that of the first plurality of diffuse particles or the second plurality of diffuse particles; and the third plurality of diffuse particles are arranged in the second sub-region at a concentration lower than that of one or more of the first plurality of diffuse particles and the second plurality of diffuse particles.

20. The light-emitting diode display of claim 16, wherein the support structure includes a lead frame structure having a housing, and the recess is formed within the housing.

21. A light-emitting diode display as described in claim 16, wherein: The first plurality of diffuse particles includes a first surface type; the second plurality of diffuse particles includes a second surface type different from the first surface type; and the third plurality of diffuse particles includes a third surface type different from both the first surface type and the second surface type.

22. A light-emitting diode display as claimed in claim 21, wherein: The first plurality of diffuse particles comprise a first median particle size distribution ranging from 7µm to 13µm; the second plurality of diffuse particles comprise a second median particle size distribution ranging from 4µm to 5µm; and the third plurality of diffuse particles comprise a third median particle size distribution ranging from 4µm to 6µm.

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