Reflector for support structure in light emitting diode package

Abstract

A reflector for a support structure in a solid-state light emitting device including a light emitting diode (LED), particularly an LED package (48), is disclosed. The support structure includes a dielectric reflector (18) disposed relative to the LED chip (36) and conductive traces (14) patterned on a submount (12). The dielectric reflector includes a multiple dielectric layer structure forming a distributed Bragg reflector (DBR), or in some cases, an aperiodic Bragg reflector. Such a dielectric reflector (18) may be disposed over one or more of the conductive traces (14) and portions of the submount (12) not covered by the conductive traces, improving reflectivity across a range of wavelengths provided by the LED chip, including wavelengths in the ultraviolet (UV) spectrum. A cover structure (38) is further provided for each of the disclosed LED packages (34, 42, 44, 46, 48, 50, 52, 54, 56, 60, 62, 64).

Description

[Technical Field]

[0001] This invention relates to solid state light emitting devices, including light emitting diodes (LEDs), and more particularly to reflectors for support structures in LED packages. [Background technology]

[0002]

[0002] Solid-state light-emitting devices, such as light-emitting diodes (LEDs), are finding increasing use in both consumer and commercial applications. Advances in LED technology have resulted in light sources that are highly efficient, mechanically robust, and long-life. Modern LEDs are therefore enabling a variety of new display applications and are increasingly being used for general lighting applications, frequently replacing incandescent and fluorescent light sources.

[0003]

[0003] An LED is a solid-state device that converts electrical energy into light and typically contains one or more active layers (or active regions) of semiconductor material disposed between oppositely doped n-type and p-type layers. When a bias is applied across the doped layers, holes and electrons are injected into the active layer(s), where they recombine to produce light, such as visible or ultraviolet light. An LED chip typically contains an active region that may be fabricated from, for example, silicon carbide, gallium nitride, gallium phosphide, aluminum nitride, or gallium arsenide-based materials, and / or from organic semiconductor materials. Photons generated by the active region travel in all directions.

[0004]

[0004] It is typically desirable to operate LEDs at the highest possible luminous efficiency, which can be measured by the luminous intensity (e.g., lumens per watt) relative to the output power. A practical goal for increasing luminous efficiency is to maximize the extraction of light emitted by the active region in the desired direction of light transmission. The light extraction and external quantum efficiency of LEDs can be limited by several factors, including internal reflection. LED packages have been developed to provide mechanical support, electrical connections, and encapsulation for the LED emitter. Light emitted from the surface of the LED emitter can interact with corresponding LED package elements or surfaces, increasing the opportunity for light loss. Additionally, various operating conditions and wavelengths of emitted light can degrade various materials traditionally used for LED packages. Therefore, there is a challenge in achieving high luminous efficiency in LED packages while producing high-quality light with desirable luminous characteristics.

[0005]

[0005] The art continues to seek improved LEDs and solid state light emitting devices with desirable lighting characteristics that can overcome the challenges associated with conventional light emitting devices. Summary of the Invention [Means for solving the problem]

[0006] The present invention relates to solid-state light emitting devices, including light emitting diodes (LEDs), and more particularly to a reflector for a support structure in an LED package. The support structure includes a dielectric reflector disposed relative to the LED chip and conductive traces patterned on a submount. The dielectric reflector includes a multi-dielectric layer structure that forms a distributed Bragg reflector, or in some cases, an aperiodic Bragg reflector. Such a dielectric reflector can be disposed on one or more of the conductive traces and on portions of the submount not covered by the conductive traces, and provides high reflectivity over a range of wavelengths provided by the LED chip, including wavelengths in the ultraviolet spectrum.

[0007] In one aspect, an LED package includes a submount having a first surface and a second surface opposite the first surface, at least one LED chip on the first surface of the submount, a cover structure disposed over the at least one LED chip, a patterned trace on the first surface of the submount, the cover structure attached to the patterned trace in a cover structure mounting area outside of the at least one die attach pad, and a dielectric reflector on a portion of the patterned trace between the at least one die attach pad and the cover structure mounting area, the dielectric reflector comprising a distributed Bragg reflector. In certain embodiments, the distributed Bragg reflector is an aperiodic distributed Bragg reflector. In certain embodiments, the aperiodic distributed Bragg reflector comprises a plurality of dielectric layers, each dielectric layer of the plurality of dielectric layers having a unique optical thickness relative to the other dielectric layers of the plurality of dielectric layers. In certain embodiments, the plurality of dielectric layers comprises dielectric layers alternating between a first material type and a second material type. In certain embodiments, there is a dielectric reflector on the portion of the submount not covered by the pattern trace and the at least one LED chip. In certain embodiments, a dielectric reflector is further disposed between the at least one LED chip and the submount in a gap formed by the pattern trace along the at least one die attach pad. In certain embodiments, the at least one LED chip is configured to provide a peak wavelength in the range of 200 nm to 400 nm.

[0008] In another aspect, an LED package includes a submount having a first surface and a second surface opposite the first surface; at least one LED chip on the first surface of the submount; a cover structure disposed over the at least one LED chip, the cover structure mounted to the submount at a cover structure mounting region spaced from a peripheral boundary of the at least one LED chip; a pattern trace on the first surface of the submount, the pattern trace forming at least one die attach pad for the at least one LED chip; and a dielectric reflector on a portion of the submount laterally adjacent to the pattern trace, the dielectric reflector comprising a distributed Bragg reflector. In certain embodiments, the dielectric reflector is further disposed on a portion of the pattern trace. In certain embodiments, the dielectric reflector is further disposed between the cover structure and the submount in the cover structure mounting region. In certain embodiments, the distributed Bragg reflector is a non-periodic distributed Bragg reflector, the non-periodic distributed Bragg reflector comprising a plurality of dielectric layers, each dielectric layer of the plurality of dielectric layers having a unique optical thickness relative to other dielectric layers of the plurality of dielectric layers. In certain embodiments, the plurality of dielectric layers comprises alternating dielectric layers of a first material type and a second material type. In certain embodiments, a dielectric layer having a greatest optical thickness among the plurality of dielectric layers is located spaced apart from a top surface of the aperiodic distributed Bragg reflector and within the aperiodic distributed Bragg reflector. In certain embodiments, the at least one LED chip is configured to provide a peak wavelength in the range of 200 nm to 400 nm.

[0009] In another aspect, an LED package includes a submount having a first surface and a second surface opposite the first surface, at least one LED chip on the first surface of the submount, a pattern trace on the first surface of the submount, and a dielectric reflector on a portion of the pattern trace and on a portion of the submount laterally adjacent to the pattern trace, the dielectric reflector comprising a distributed Bragg reflector. In certain embodiments, the distributed Bragg reflector is an aperiodic distributed Bragg reflector. In certain embodiments, the aperiodic distributed Bragg reflector includes a plurality of dielectric layers, each dielectric layer of the plurality of dielectric layers having a unique optical thickness relative to the other dielectric layers of the plurality of dielectric layers. In certain embodiments, the plurality of dielectric layers includes alternating dielectric layers of a first material type and a second material type. In certain embodiments, the dielectric layer of the plurality of dielectric layers having the greatest optical thickness is located spaced apart from the top surface of the aperiodic distributed Bragg reflector and within the aperiodic distributed Bragg reflector. In certain embodiments, the pattern trace includes at least one die attach pad for the at least one LED chip, and a dielectric reflector is further disposed between the at least one LED chip and the submount in a gap formed by the pattern trace along the at least one die attach pad. In certain embodiments, the at least one LED chip is configured to provide a peak wavelength in the range of 200 nm to 400 nm. The LED package may further include a cover structure disposed above the submount to form a cavity above the at least one LED chip. The LED package may further include a reflector structure disposed between the cover structure and the submount, with sidewalls of the reflector structure surrounding a portion of the cavity. In certain embodiments, a dielectric reflector is disposed on a sidewall of the reflector structure. In certain embodiments, a dielectric reflector is disposed between the reflector structure and the submount.

[0010] In other aspects, any of the foregoing aspects may be combined individually or together, and / or with various separate aspects and features described herein to further advantage. Any of the various features and elements disclosed herein may be combined with one or more of the other disclosed features and elements, unless indicated to the contrary herein.

[0011] Those skilled in the art will appreciate the scope of the present disclosure and realize additional aspects thereof after reading the following detailed description of the preferred embodiments in conjunction with the accompanying drawings.

[0012] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate several aspects of the disclosure and, together with the description, serve to explain the principles of the disclosure. [Brief explanation of the drawings]

[0012] [Figure 1]

[0013] FIG. 1 is a top view of a portion of a light emitting diode (LED) package including a portion of first pattern traces, collectively referred to herein as first pattern traces, provided on a submount and a dielectric reflector in accordance with the principles of the present disclosure. [Figure 2]

[0014] 2 is a top view of a portion of an LED package similar to that of FIG. 1 for an alternative layout of a dielectric reflector. [Figure 3]

[0015] FIG. 2 is a cross-sectional view of an exemplary dielectric reflector that may be provided for any embodiment of the present disclosure. [Figure 4]

[0016] FIG. 4A is a cross-sectional view of a structure including a first pattern trace and a dielectric reflector.

[0017] FIG. 4B is a cross-sectional view of a structure with an alternative arrangement of the first pattern trace and dielectric reflector. [Figure 5]

[0018] 5A is a cross-sectional view of an LED package cut along a portion of the LED package similar to section line AA of FIG. 1, the LED package being assembled with at least one LED chip and a cover structure in accordance with the principles of the present disclosure.

[0019] 5B is a cross-sectional view of the LED package of FIG. 5A taken along a portion of the LED package similar to section line BB in FIG. 1 in a region outside the LED chip. [Figure 6]

[0020] FIG. 6A is a cross-sectional view of an LED package similar to that of FIGS. 5A and 5B, but with an alternative arrangement of the cover structure.

[0021] 6B is a cross-sectional view of the LED package of FIG. 6A taken along a portion of the LED package, similar to section line BB in FIG. 1, in a region outside the LED chip. [Figure 7]

[0022] 7A is a cross-sectional view of an LED package cut along a portion of the LED package similar to section line AA in FIG. 1, in which a dielectric reflector is provided between the cover structure and the submount in the cover structure mounting area.

[0023] 7B is a cross-sectional view of the LED package of FIG. 7A taken along a portion of the LED package similar to section line BB of FIG. [Figure 8]

[0024] FIG. 8A is a cross-sectional view of an LED package similar to that of FIGS. 6A and 6B, in which a dielectric reflector is provided between the cover structure and the submount in the cover structure mounting area.

[0025] 8B is a cross-sectional view of the LED package of FIG. 8A taken along a portion of the LED package, similar to section line BB in FIG. 1, in a region outside the LED chip. [Figure 9]

[0026] 5B is a cross-sectional view of an LED package similar to that of FIG. 5A, further comprising a dielectric reflector on a portion of the submount laterally adjacent the first pattern trace. [Figure 10]

[0027] 7B is a cross-sectional view of an LED package similar to that of FIG. 7A, further comprising a dielectric reflector on a portion of the submount laterally adjacent the first pattern trace. [Figure 11]

[0028] 2 is a cross-sectional view of the LED package taken along a portion of the LED package similar to section line AA in FIG. 1, where the cover structure mounting area does not include a first pattern trace. [Figure 12]

[0029] 12 is a cross-sectional view of an LED package similar to that of FIG. 11 except that the dielectric reflector is not located within the cover structure mounting area. [Figure 13]

[0030] 2 is a cross-sectional view of an LED package taken along a portion of the LED package similar to section line AA in FIG. 1, the LED package including a reflector structure disposed between a cover structure and a submount. [Figure 14]

[0031] 14 is a cross-sectional view of an LED package similar to that of FIG. 13, in which a dielectric reflector extends over the first pattern trace at a location between the reflector structure and the submount. [Figure 15]

[0032] 14 is a cross-sectional view of an LED package similar to that of FIG. 13, in which a dielectric reflector extends along the sidewalls of the reflector structure. [Figure 16]

[0033] 16 is a cross-sectional view of an LED package similar to that of FIG. 15, in which a dielectric reflector extends along the sidewall of the reflector structure and between the reflector structure and the first pattern trace. DETAILED DESCRIPTION OF THE INVENTION

[0013]

[0034] The embodiments described below represent the information necessary to enable one skilled in the art to realize the embodiments and illustrate the best modes for achieving them. Upon reading the following description in conjunction with the accompanying drawings, one skilled in the art will understand the concepts of the present disclosure and will recognize applications of these concepts not specifically addressed herein. It is to be understood that these concepts and applications are within the scope of this disclosure and the appended claims.

[0014]

[0035] In this specification, terms such as first, second, etc. may be used to describe various elements, but it will be understood that these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first element can be referred to as a second element, and similarly, a second element can be referred to as a first element, without departing from the scope of the present disclosure. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0015]

[0036] When an element such as a layer, region, or substrate is referred to as being "on" or extending "upon" another element, it will be understood that the element may be directly on or extending directly onto the other element, or that intervening elements may 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. Similarly, when an element such as a layer, region, or substrate is referred to as being "above" or extending "upon" another element, it will be understood that the element may be directly on or extending directly onto the other element, or that intervening elements may 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. It will also be understood that when an element is referred to as being "connected" or "coupled" to another element, the element may be directly connected or coupled to the other element, or there may be intervening elements. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present.

[0016]

[0037] Relative terms such as "lower" or "above" or "upper" or "bottom" or "horizontal" or "vertical" may be used herein to describe the relationship of one element, layer, or region to another element, layer, or region, as illustrated in the figures. It is understood that these terms, and those discussed above, are intended to encompass various orientations of the device in addition to the orientation depicted in the figures.

[0017]

[0038] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, it will be understood that the terms "comprises," "comprising," "including," and / or "comprising," as used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0018]

[0039] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Furthermore, it will be understood that terms used herein should be interpreted as having a meaning consistent with the meaning in the context of this specification and the related art, and should not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0019]

[0040] Embodiments are described herein with reference to schematic diagrams of embodiments of the present disclosure. As such, actual dimensions of layers and elements may vary, and variations from the shapes of the schematic diagrams are expected, for example, as a result of manufacturing techniques and / or tolerances. For example, regions illustrated or described as square or rectangular may have rounded or curved features, and regions depicted as straight lines may have irregularities. Accordingly, regions illustrated in the drawings are schematic, and their shapes are not intended to illustrate the exact shape of a region of a device or to limit the scope of the disclosure. Additionally, the size of structures or regions may be exaggerated relative to other structures or regions for illustrative purposes and, therefore, are provided to illustrate the general structure of the present subject matter and may or may not be drawn to scale. Elements common between figures may be illustrated with common element numbers herein and may not be described again later.

[0020]

[0041] The present disclosure relates to solid-state light emitting devices, including light emitting diodes (LEDs), and in particular to a reflector for a support structure in an LED package. The support structure includes a dielectric reflector disposed relative to the LED chip and conductive traces patterned on a submount. The dielectric reflector includes a multiple dielectric layer structure that forms a distributed Bragg reflector, or in some cases, an aperiodic Bragg reflector. Such a dielectric reflector may be disposed on one or more of the conductive traces and on portions of the submount not covered by the conductive traces, to improve reflectivity over a range of wavelengths provided by the LED chip, including wavelengths in the ultraviolet (UV) spectrum.

[0021]

[0042] Before delving into the specific details of various aspects of the present disclosure, an overview of the various elements that may be included in an exemplary LED package of the present disclosure is provided for context. An LED chip typically includes an active LED structure or region that may have a number of different semiconductor layers arranged in various ways. The fabrication and operation of LEDs and their active structures are generally known in the art and will be discussed only briefly herein. The layers of the active LED structure can be fabricated using known processes, with a suitable process being fabrication using metalorganic chemical vapor deposition. The layers of the active LED structure can include many different layers, and typically include an active layer sandwiched between n-type and p-type oppositely doped epitaxial layers, all of which are formed sequentially on a growth substrate. It is understood that the active LED structure can also include additional layers and elements, including, but not limited to, buffer layers, nucleation layers, superlattice structures, undoped layers, cladding layers, contact layers, current spreading layers, light extraction layers, and other elements. The active layer can include a single quantum well, multiple quantum wells, a double heterostructure, or a superlattice structure.

[0022]

[0043] The active LED structure can be fabricated from different material systems, some of which are III-nitride-based material systems. III-nitrides refer to semiconductor compounds formed from nitrogen (N) and elements from group III of the periodic table, usually aluminum (Al), gallium (Ga), and indium (In). Gallium nitride (GaN) is a common binary compound. III-nitrides also refer to ternary and quaternary compounds such as aluminum gallium nitride (AIGaN), indium gallium nitride (InGaN), and aluminum indium gallium nitride (AlnGaN). Other material systems include silicon carbide (SiC), organic semiconductor materials, and other III-V systems such as gallium phosphide (GaP), gallium arsenide (GaAs), and related compounds.

[0023]

[0044] The active LED structure can be grown on a growth substrate, which can include many materials, such as sapphire, SiC, aluminum nitride (AlN), and GaN. SiC has certain advantages, such as a closer crystal lattice match with III-nitrides than other substrates, resulting in high-quality III-nitride films. SiC also has very high thermal conductivity, so the total output power of III-nitride devices on SiC is not limited by the heat dissipation of the substrate. Sapphire is another common substrate for III-nitrides and also has certain advantages, such as lower cost, an established manufacturing process, and good optical properties with good light transmission.

[0024]

[0045] Different embodiments of the active LED structure can emit light of different wavelengths depending on the configuration of the active layer, n-type layer, and p-type layer. In some embodiments, the active LED structure emits blue light with a peak wavelength range of approximately 430 nanometers (nm) to 480 nm. In other embodiments, the active LED structure emits green light with a peak wavelength range of 500 nm to 570 nm. In other embodiments, the active LED structure emits red light with a peak wavelength range of 600 nm to 650 nm. In certain embodiments, the active LED structure can be configured to emit light outside the visible spectrum, including one or more portions of the UV spectrum. The UV spectrum is typically divided into three wavelength range categories, designated by the letters A, B, and C. Thus, UV-A light is typically defined as a peak wavelength range of 315 nm to 400 nm, UV-B is typically defined as a peak wavelength range of 280 nm to 315 nm, and UV-C is typically defined as a peak wavelength range of 100 nm to 280 nm. UV LEDs are of particular interest for applications related to disinfection of microorganisms in air, water, and surfaces, among others. In other applications, UV LEDs may be provided with one or more lumiphoric materials to provide the LED package with an aggregated light emission having a broad spectrum and improved color quality for visible light applications.

[0025]

[0046] Light emitted from the active layer or region of an LED chip can typically travel in a variety of directions. For targeted applications, an internal mirror or external reflective surface can be used to redirect as much light as possible toward the desired emission direction. The internal mirror can include single or multiple layers. Some multilayer mirrors include a metallic reflective layer and a dielectric reflective layer, with the dielectric reflective layer disposed between the metallic reflective layer and multiple semiconductor layers. A passivation layer is disposed between the metallic reflective layer and first and second electrical contacts, with the first electrical contact disposed in conductive communication with the first semiconductor layer and the second electrical contact disposed in conductive communication with the second semiconductor layer. For single-layer or multilayer mirrors that include surfaces exhibiting less than 100% reflectivity, some light may be absorbed by the mirror. Additionally, light redirected through the active LED structure may be absorbed by other layers or elements within the LED chip.

[0026]

[0047] As used herein, a layer or region of a light-emitting device may be considered “transparent” if at least 80% of the emitted light impinging on that layer or region passes through that layer or region and exits. Additionally, as used herein, a layer or region of an LED may be considered “reflective” or embody a “mirror” or “reflector” if at least 80% of the emitted light impinging on that layer or region is reflected. In some embodiments, the emitted light comprises visible light, such as in blue and / or green LEDs, with or without luminescent materials. In other embodiments, the emitted light may comprise non-visible light. For example, in the context of GaN-based blue and / or green LEDs, silver (Ag) may be considered a reflective material (e.g., at least 80% reflective). For UV LEDs, appropriate materials may be selected to achieve a desired, in some embodiments, high reflectivity and / or a desired, in some embodiments, low absorption. In certain embodiments, a “light-transmitting” material may be configured to transmit at least 50% of the emitted light of a desired wavelength.

[0027]

[0048] The present disclosure may be useful for LED chips having various geometries, including flip-chip geometries. Flip-chip LED chip structures typically include anode and cathode connections formed from the same side or surface of the LED chip. The anode and cathode sides are typically structured as mounting surfaces of the LED chip for flip-chip mounting to another surface, such as a printed circuit board. In this regard, the anode and cathode connections on the mounting surface serve to mechanically and electrically bond the LED chip to the other surface. When flip-chip mounted, the opposite side or surface of the LED chip corresponds to the light-emitting surface oriented in the intended direction of light emission. In certain embodiments, when flip-chip mounted, the growth substrate of the LED chip may form and / or be adjacent to the light-emitting surface. During chip fabrication, active LED structures may be epitaxially grown on the growth substrate.

[0028]

[0049] According to embodiments of the present disclosure, an LED package may include one or more elements, such as a wavelength-converting luminescent material or phosphor, an encapsulant, a light-altering material, a lens, and electrical contacts, among others, provided with one or more LED chips. In certain embodiments, the LED package may include a support member, such as a submount or lead frame. Light-altering 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. As used herein, light-altering materials may include many different materials, including light-reflecting materials that reflect or redirect light, light-absorbing materials that absorb light, and materials that act as thixotropic agents.

[0029]

[0050] Aspects of the present disclosure include support structures for LED packages. A support structure can refer to a structure of an LED package that supports one or more other elements of the LED package, including, but not limited to, an LED chip and a cover structure. In certain embodiments, the support structure can include a submount on which the LED chip is mounted. Suitable materials for the submount include, but are not limited to, ceramic materials such as aluminum oxide or alumina, AlN, or organic insulators such as polyimide (PI) or polyphthalamide (PPA). In other embodiments, the submount can comprise a printed circuit board (PCB), sapphire, Si, or any other suitable material. For PCB embodiments, different types of PCBs can be used, such as standard FR-4 PCBs, metal-core PCBs, or any other type of PCB. In still further embodiments, the support structure can embody a leadframe structure. Aspects of the present disclosure are provided in the context of support structures for LED chips that can emit light in any number of wavelength ranges, including wavelengths within the UV and / or visible light spectrum.

[0030]

[0051] UV LEDs have attracted particular attention in applications related to disinfecting microorganisms, particularly in air, water, and on surfaces. In other applications, UV LEDs may be provided with one or more luminescent materials to provide a concentrated, broad emission with improved color quality across the visible spectrum. Certain embodiments of the present disclosure may be well-suited for applications in which LED emission is provided in one or more of the UV-A, UV-B, and UV-C wavelength ranges. Low peak wavelengths, such as those in one or more of the UV-B and UV-C wavelength ranges, may have high energy levels, potentially leading to decomposition of materials commonly used in other LED packages, including silicon, polymers, and / or other organic materials commonly used as encapsulants and / or binders for reflective particles and / or luminescent materials. Cover structures for UV-based LED packages may be required to provide protection from exposure to the external environment, such as by providing a hermetic seal. As used herein, a hermetic seal generally refers to a seal that is airtight and waterproof and prevents the passage of air, gas, and / or liquid. In this regard, organic materials such as silicon and epoxy are not considered hermetic seals because they are air-permeable. In this manner, the cover structure of the UV LED may include at least one of glass, quartz, and / or ceramic materials that reduce damage from exposure to UV radiation, while also being attached or otherwise bonded to the package support structure to hermetically seal the underlying LED chip.

[0031]

[0052] The support structure of the LED package may include one or more conductive materials that can provide electrical connection to the LED chip. The conductive materials may be provided as metal traces or patterned metal traces on a submount, or the conductive materials may form a leadframe structure with or without a corresponding submount. The conductive materials may include any number of materials, including copper (Cu) or its alloys, nickel (Ni) or its alloys, nickel chromium (NiCr), gold (Au) or its alloys, electroless Au, electroless silver (Ag), NiAg, Al or its alloys, titanium tungsten (TiW), titanium tungsten nitride (TiWN), electroless nickel electroless palladium immersion gold (ENEPIG), electroless nickel immersion gold (ENIG), hot air solder leveling (HASL), and organic solderability preservative (OSP). In certain embodiments, the conductive material may include ENEPIG or ENIG with a gold (Au) top layer. In other embodiments, the conductive material may include a silver (Ag) top layer. Au and Ag have low reflectivity (e.g., about 20% to 40% reflectivity) in the UV-B and UV-C wavelength spectrum. In such embodiments, a layer with increased reflectivity to UV radiation, such as Al, may be disposed on or otherwise incorporated into the conductive material.

[0032]

[0053] In accordance with the principles disclosed herein, the placement of a dielectric reflector further enhances the reflectivity of an LED package. In certain embodiments, the dielectric reflector can be configured to enhance reflectivity for specific wavelengths, such as UV wavelengths, while at the same time being composed of a material that is resistant to degradation associated with UV exposure. As described in more detail below, the dielectric reflector can include a multilayer structure that forms a distributed Bragg reflector or even an aperiodic distributed Bragg reflector. Such a dielectric reflector can be provided on the patterned metal traces and / or on portions of the package submount between the patterned metal traces, thereby increasing the reflective surface without electrically shorting adjacent electrical traces.

[0033]

[0054] FIG. 1 is a top view illustrating a portion of an LED package 10 including first pattern trace portions 14-1 through 14-3, collectively referred to herein as first pattern trace 14, and a dielectric reflector 18 provided on a submount 12 in accordance with the principles of the present disclosure. As used herein, submount 12 is a form of support structure for LED package 10. First pattern trace 14 may form several discontinuous portions, i.e., traces 14-1 through 14-3, on submount 12. For example, the discontinuous portions of first pattern trace 14, i.e., traces 14-2 and 14-3, may form a die attach pad for an LED chip, with one of discontinuous portions 14-2, 14-3 forming the anode pad of the die attach pad and the other of discontinuous portions 14-2, 14-3 forming the corresponding cathode pad of the die attach pad. In this manner, an LED chip may be flip-chip mounted to the die attach pad. Vias 16 may be provided that electrically connect discontinuous portions 14-2, 14-3 to corresponding electrical connections on the rear or bottom surface of submount 12. In certain embodiments, protrusions 14-2′, 14-3′ of discontinuous portions 14-2, 14-3 may extend away from the die attach pad area to form an attachment area for another element, such as an electrical overstress element (e.g., an ESD chip, a Zener diode, etc.), that may be coupled in parallel with the LED chip. As illustrated, portions of submount 12 between and around discontinuous portions 14-2, 14-3 are free of or not covered by first pattern traces 14. In certain embodiments, discontinuous portions 14-1 may be provided on submount 12 around discontinuous portions 14-2, 14-3.

[0034]

[0055] The first pattern trace 14 may include one or more layers of copper, gold, silver, ENEPIG, ENIG, etc., that reduce reflectivity for UV-B and UV-C radiation. In certain embodiments, a dielectric reflector 18 is selectively provided on the first pattern trace 14. In FIG. 1 , the dielectric reflector 18 is provided on a portion of the discontinuous portion 14-1 (as better illustrated in the cross-sectional views of FIGS. 5A through 6B ). The dielectric reflector 18 may include any material that exhibits high reflectivity, such as at least 60% reflectivity, at least 80% reflectivity, or at least 90% reflectivity, for specific LED radiation compared to the first pattern trace 14. For example, for UV-B and UV-C wavelengths, aluminum may provide at least 90% reflectivity, while the material of the first pattern trace 14 may exhibit less than 40% reflectivity. As will be described in detail later, the cover structure may be mounted to the submount 12 using a metallurgical bonding material. The dielectric reflector 18 may exhibit improved reflectivity, while the metallurgical bonding material may enhance adhesion to the material of the first pattern trace 14. In this regard, the dielectric reflector 18 may be selectively disposed on the first pattern trace 14 to allow the cover structure mounting area to have direct access to the first pattern trace 14. In FIG. 1 , the portion of the discontinuous portion 14-1 that is absent or not covered by the dielectric reflector 18 forms a cover structure mounting area disposed around the surface of the submount 12. Therefore, the cover structure of the LED package 10 may be mounted such that the cover structure contacts the submount 12 only at the cover structure mounting area. In this manner, the dielectric reflector 18 may be disposed on a portion of the first pattern trace 14 that is between the die attach pads (e.g., 14-2, 14-3) and the cover structure mounting area. As will be described in more detail below, in other embodiments, the dielectric reflector 18 may alternatively extend over the cover structure mounting area, so that all or substantially all of the submount 12 outside the LED chip die attach pad and electrical overstress element mounting area is covered by the dielectric reflector 18.

[0035]

[0056] FIG. 2 is a top view of a portion of an LED package 20 similar to the LED package 10 of FIG. 1 , with an alternative layout of the dielectric reflector 18. As illustrated, the dielectric reflector 18 forms a circular shape on the discontinuous portion 14-1 of the first pattern trace 14. In this regard, the cover structure mounting area formed by the area of ​​the discontinuous portion 14-1 that is absent or not covered by the dielectric reflector 18 is also provided with a corresponding circular pattern. Such an arrangement may be suitable for a cover structure including a domed lens mounted above the submount 12. As in FIG. 1 , the dielectric reflector 18 can extend to the periphery of the submount 12, covering all or substantially all of the submount 12 outside the die attach pad of the LED chip, with the mounting area for the electrical overstress element being covered by the dielectric reflector 18.

[0036]

[0057] FIG. 3 is a cross-sectional view of an exemplary dielectric reflector 18 that may be provided for any of the previously described or later embodiments of the present disclosure. The dielectric reflector 18 may include multiple dielectric layers 18-1 through 18-9 configured to enhance reflection of light from an associated LED chip. In certain embodiments, the materials and / or thicknesses of the individual dielectric layers 18-1 through 18-9 may be tailored to provide varying optical thicknesses. Optical thickness, also referred to as optical path length, may be defined as the product of the refractive index of a material and the geometric length of the optical path through the layer. Thus, the optical thickness of the individual layers 18-1 through 18-9 may be altered by increasing or decreasing the actual layer thickness and / or by providing a layer with a different material type than another layer of the layers 18-1 through 18-9. In certain embodiments, the dielectric layers 18-1 through 18-9 may form alternating layers of varying optical thickness such that the dielectric reflector 18 comprises a distributed Bragg reflector. For example, each of the dielectric layers 18-1, 18-3, 18-5, 18-7 and 18-9 may comprise a first material type, and each of the dielectric layers 18-2, 18-4, 18-6 and 18-8 may comprise a second material type having a different refractive index than the first material type.

[0037]

[0058] The dielectric reflector 18 may also form a non-periodically distributed Bragg reflector in which the optical thickness of each of the dielectric layers 18-1 through 18-9 varies across the dielectric reflector 18. In certain embodiments, each individual dielectric layer 18-1 through 18-9 may have a unique optical thickness compared to the other dielectric layers 18-1 through 18-9. As an example, each of the dielectric layers 18-1, 18-3, 18-5, 18-7, and 18-9 may comprise a first material type, but the relative thicknesses of the dielectric layers 18-1, 18-3, 18-5, 18-7, and 18-9 may vary. In certain embodiments, the dielectric layer 18-3 within the dielectric reflector 18 is the thickest layer, but the other dielectric layers 18-1, 18-5, 18-7, and 18-9 may also have thicknesses that vary relative to one another. Similarly, the dielectric layers 18-2, 18-4, 18-6, and 18-8 may comprise a second material type having a different refractive index than the first material type, and one or more of the dielectric layers 18-2, 18-4, 18-6, and 18-8 may have thicknesses that vary relative to one another. In this manner, the interfaces between each pair of adjacent dielectric layers 18-1 through 18-9 may provide different total internal reflection (TIR) ​​responses based on the angle and wavelength of the incident light. Generally, a dielectric layer (e.g., 18-3) with a greater optical thickness promotes TIR of light at shallower angles of incidence than another layer (e.g., 18-1) with a thinner optical thickness. Thus, it may be advantageous to position the layer with the greatest optical thickness (e.g., 18-3) within the dielectric reflector 18, away from the top surface of the dielectric reflector 18, or at the bottom of the dielectric reflector 18, so that light at higher angles of incidence can be redirected more quickly, avoiding potential light loss due to internal absorption. Thus, multiple layers with varying optical thicknesses allow some layers to reflect more light at shallower angles of incidence and other layers to reflect more light at larger angles of incidence, improving total internal reflection across all angles in the multiple layers.

[0038]

[0059] The materials of the dielectric layers 18-1 through 18-9 may comprise aluminum oxide (Al2O3), hafnium oxide (HfO2), silicon dioxide (SiO2), zirconium dioxide (ZrO2), and / or silicon nitride, among others. In the context of UV radiation, dielectric layers 18-1 through 18-9 with greater optical thickness contrast and / or greater refractive index difference structures can be used to appropriately redirect such wavelengths. As an example, the ability to individually adjust the optical thickness of each of the dielectric layers 18-1 through 18-9 can provide reflectance values ​​of at least 97%, or in the range of 97% to 99%, for UV radiation in the range of 250 nm to 315 nm, or in the range of 200 nm to 315 nm. Such reflectance values ​​exceed traditional metallic reflective layers commonly used in UV LED packages. In still further embodiments, the ability to individually adjust the optical thickness of each of the dielectric layers 18-1 through 18-9 may also provide the ability to specifically adjust the emission pattern and / or wavelength range of the LED package.

[0039]

[0060] FIG. 4A is a cross-sectional view of a structure 22 including a first pattern trace 14 and a dielectric reflector 18 according to certain embodiments. For illustrative purposes, the dielectric reflector 18 is depicted without the details of FIG. 3, but it is understood that the dielectric reflector 18 may include any of the layers 18-1 through 18-9 described above with respect to FIG. 3. FIG. 4A may represent any embodiment of the present disclosure from the region where the dielectric reflector 18 is formed on the first pattern trace 14. As illustrated, the first pattern trace 14 may embody a multi-layer structure, such as a first layer 24, a second layer 26, and a third layer 28 of the first pattern trace 14. In certain embodiments, the first layer 24 may include a layer of Cu and / or an alloy thereof, the second layer 26 may include one or more layers of Ni, palladium (Pd), or an alloy thereof, and the third layer 28 may comprise a layer of Au. The first patterned traces 14 may include an electrolyte layer, which may be collectively referred to as an ENEPIG layer. In certain embodiments, a thin adhesion layer including titanium (Ti) and / or its alloys may be provided on the bottom surface of the first layer 24 for adhesion to an underlying submount.

[0040]

[0061] 4B is a cross-sectional view 32 of a structure 30 with an alternative arrangement of first pattern traces 14 and dielectric reflector 18. In FIG. 4B, structure 30 includes a layer 31 that occupies most or even all of first pattern traces 14. In certain embodiments, a thin adhesion layer may be provided on the bottom side of layer 31. Layer 31 may comprise a layer of Au in Cu-free embodiments. Alternatively, layer 31 may comprise a layer of Cu with a thin layer of silver on the top side at the interface with dielectric reflector 18.

[0041]

[0062] 5A through 16 are cross-sectional views of LED packages having various configurations of the dielectric reflector 18 and first pattern trace 14 described above. Figures 5A through 16 are illustrated using the first pattern trace 14 described above for Figure 4A. However, it is understood that the first pattern trace 14 in each of Figures 5A through 16 may alternatively have the structure described above for Figure 4B. In addition, the dielectric reflector 18 in Figures 5A through 16 may have any of the structures described above for Figure 3.

[0042]

[0063] FIG. 5A is a cross-sectional view of an LED package 34 taken along a portion of the LED package 34 similar to section line AA in FIG. 1 , where the LED package 34 is assembled with at least one LED chip 36 and a cover structure 38 in accordance with the principles of the present disclosure. Depending on the embodiment and target application, the LED chip 36 may be configured to emit a peak wavelength in either the visible or UV spectrum, including a peak wavelength in the range of 200 nm to 750 nm or in the range of 200 nm to 400 nm. As illustrated, the LED chip 36 is mounted on a die attach pad formed by a portion of the first pattern trace 14 (e.g., portions 14-2 and 14-3 in FIG. 1 ). Vias 16 may extend throughout the thickness of the submount 12 and provide electrical connection between the LED chip 36 on the top surface of the submount 12 and corresponding portions of the second pattern trace 15 on the bottom surface of the submount 12. The second pattern trace 15 may be configured to accept external electrical connections for the LED package 34. Additionally, second pattern trace 15 may be provided with sufficient surface area across the bottom surface of submount 12 to improve heat dissipation of LED package 34. In certain embodiments, second pattern trace 15 may include a similar arrangement to first pattern trace 14, such that first layer 24, second layer 26, and third layer 28 are sequentially disposed on the bottom surface of submount 12. In other embodiments, second pattern trace 15 may include a different structure than first pattern trace 14.

[0043]

[0064] The cover structure 38 may be formed above the LED chip 36 and attached to the first pattern traces 14 at or near the periphery of the LED package 34. Such an attachment area may be referred to as a cover structure mounting area. The cover structure 38 may include vertical sidewalls that extend to the submount 12 at one or more locations below the height of the LED chip 36. In this regard, the cover structure 38 may form a cavity 40 or opening above the LED chip 36 and above the submount 12. In certain embodiments, the cavity 40 may be filled with air and / or nitrogen. In certain embodiments, depending on how the cover structure 38 is attached, the cavity 40 may be evacuated to the surrounding atmosphere. In certain embodiments, the cover structure 38 forms an airtight seal for the LED package 34. As illustrated, a cover structure mounting area is defined where the cover structure 38 is attached to the first pattern traces 14 at or near the periphery of the submount 12. In certain embodiments, the cover structure 38 may form a dome-shaped or hemispherical lens for directing light emission from the LED chip 36. In certain embodiments, the lens may have many different shapes, depending on the desired shape of the light output. Suitable shapes include hemispherical, elliptical, ellipsoid bullet, cubic, flat, hex-shaped, and square. In certain embodiments, suitable shapes include both curved and flat surfaces, such as a hemispherical or curved top and flat sides. As illustrated in FIG. 5A , the edges of the curved top of the cover structure 38 may be aligned with the corresponding edges of the cavity 40.

[0044]

[0065] While the material of the first pattern trace 14 may provide good adhesion for mounting the LED chip 36 and cover structure 38, the material of the first pattern trace 14 may have inadequate reflectivity, particularly in embodiments in which the LED chip 36 provides UV-B and / or UV-C light. In this regard, a dielectric reflector 18 is provided on a portion of the first pattern trace 14 between the die attach pad of the LED chip 36 and the cover structure mounting area. By disposing the dielectric reflector 18 above the portion of the first pattern trace 14 exposed within the cavity 40, reflectivity is improved, increasing light emission from the LED package 34. While the dielectric reflector 18 may be configured for all wavelengths of light, including visible and UV, the dielectric reflector 18 may be particularly useful for UV applications in which conventional insulating reflective materials, such as white solder masks, may degrade under UV radiation. As illustrated, in certain embodiments, at least a portion of the dielectric reflector 18 may be self-aligned to at least one end of the first pattern trace 14.

[0045]

[0066] 5B is a cross-sectional view of the LED package 34 of FIG. 5A taken along a portion of the LED package 34 similar to section line BB in FIG. 1 in a region outside the LED chip 36. As illustrated, a dielectric reflector 18 may be provided along substantially all of the first pattern traces 14 outside the LED chip 36 and within the cavity 40 to enhance reflectivity. FIGS. 5A and 5B illustrate the dielectric reflector 18 with a small gap near the cover structure 38 to ensure mounting tolerance of the cover structure 38. In other embodiments, the dielectric reflector 18 may extend completely from one end of the cavity 40 to the other without a gap.

[0046]

[0067] FIG. 6A is a cross-sectional view of an LED package 42 similar to the LED package 34 of FIGS. 5A and 5B, but with an alternative arrangement of the cover structure 38. The cross-sectional view provided in FIG. 6A is a cross-sectional view taken along a portion of the LED package 42 similar to that provided for the illustration of the LED package 34 in FIG. 5A. FIG. 6B is a cross-sectional view of the LED package 42 of FIG. 6A taken along a portion of the LED package 42, similar to section line BB in FIG. 1, in an area outside the LED chip 36. The LED package 42 is similar to the LED package 34 of FIGS. 5A and 5B, except that the cover structure 38 forms a flat or planar cover above the submount 12 with vertical sidewalls that extend to the submount 12 at a location below the height of the LED chip 36. In this regard, the LED package 42 can be provided with a lower profile for certain applications.

[0047]

[0068] FIG. 7A is a cross-sectional view of an LED package 44 taken along a portion of the LED package 44 similar to section line AA in FIG. 1 , where a dielectric reflector 18 is provided between the cover structure 38 and the submount 12 in the cover structure mounting region in accordance with the principles of the present disclosure. FIG. 7B is a cross-sectional view of the LED package 44 of FIG. 7A taken along a portion of the LED package 44 similar to section line BB in FIG. 1 . The LED package 44 is similar to the LED package 34 of FIGS. 5A and 5B , except that the dielectric reflector 18 extends between the cover structure 38 and the submount 12 in the cover structure mounting region. In this regard, the dielectric reflector 18 may cover the entire region of the first pattern trace 14 that is discontinuous with the die attach pad of the LED chip 36. Such a configuration may be suitable for embodiments in which the cover structure 38 comprises a material that does not require metallurgical attachment, such as glass. In this regard, the cover structure 38 may be mounted to a portion of the dielectric reflector 18, which may in some cases provide improved reflectivity in the cover structure mounting area of ​​the LED package 44, particularly for UV applications.

[0048]

[0069] FIG. 8A is a cross-sectional view of an LED package 46 similar to the LED package 42 of FIGS. 6A and 6B , in which a dielectric reflector 18 is provided between the cover structure 38 and the submount 12 in the cover structure mounting region. The cross-sectional view provided in FIG. 8A is a cross-sectional view taken along a portion of the LED package 46 similar to that provided for the LED package 42 in FIG. 6A . FIG. 8B is a cross-sectional view of the LED package 46 of FIG. 8A taken along a portion of the LED package 46, similar to section line BB in FIG. 1 , in a region outside the LED chip 36. The LED package 46 is similar to the LED package 44 of FIGS. 7A and 7B for an embodiment in which the cover structure 38 forms a flat or planar cover over the submount 12 and the vertical sidewalls extend to the submount 12 at a position below the height of the LED chip 36. In this regard, the LED package 46 can be provided with a lower profile for certain applications.

[0049]

[0070] FIG. 9 is a cross-sectional view of an LED package 48 similar to FIG. 5A , further including a dielectric reflector 18 on a portion of the submount 12 laterally adjacent to the first pattern trace 14. In this manner, the dielectric reflector 18 may be disposed on a portion of the submount 12 without the first pattern trace 14 therebetween. For example, a portion of the dielectric reflector 18 may be on the submount 12 in the gap between the discontinuous portions of the first pattern trace 14 (e.g., 14-2 and 14-3 in FIG. 1 ) that form the die attach pad. In this manner, the dielectric reflector 18 may be positioned between the LED chip 36 and the submount 12 to reflect downwardly propagating light toward the cover structure 38. To avoid topography differences for mounting the LED chip 36, such a portion of the dielectric reflector 18 may have a thickness less than that of the first pattern trace 14. In certain embodiments, the dielectric reflector 18 may cover a portion of the submount 12 between other discontinuous portions of the first pattern trace 14 that are outside the die attach area. In FIG. 9 , such regions are illustrated to the left and right of the LED chip 36. In this manner, all or substantially all of the portions of the floor of the cavity 40, including the top surfaces of the first pattern traces 14 and the top surfaces of the submount 12 not covered by the first pattern traces 14, can be covered with a dielectric reflector 18 to improve brightness. As further illustrated in FIG. 9 , by providing a dielectric reflector 18 within the cover structure mounting area and on the portions of the submount 12 not covered by the first pattern traces 14, the dielectric reflector 18 can effectively cover the entire submount 12 except for the portions of the first pattern traces 14 on which the LED chip 36 and optional electrical overstress elements are mounted. In certain embodiments, the cover structure 38 arrangement of FIG. 6A can be provided for the LED package 48 of FIG. 9 in combination with the dielectric reflector 18 arrangement of FIG. 9.

[0050]

[0071] 10 is a cross-sectional view of an LED package 50 similar to LED package 44 of FIG. 7A , further comprising a dielectric reflector 18 on a portion of submount 12 laterally adjacent to first pattern trace 14. In a manner similar to that described above with respect to FIG. 9 , dielectric reflector 18 may be positioned along a portion of submount 12 between discontinuous portions of first pattern trace 14, such as beneath LED chip 36 in the die attach pad gap, and / or along a portion of submount 12 adjacent to LED chip 36. Additionally, dielectric reflector 18 may extend along a portion of first pattern trace 14 such that dielectric reflector 18 is between cover structure 38 and first pattern trace 14. In this manner, cover structure 38 may be attached to dielectric reflector 18.

[0051]

[0072] FIG. 11 is a cross-sectional view of an LED package 52 taken along a portion of the LED package 52 similar to section line AA in FIG. 1 , showing that the first pattern trace 14 is not provided in the cover structure mounting region in accordance with the principles of the present disclosure. As illustrated, the first pattern trace 14 may be provided only in the region of the submount 12 that forms the die attach pad (e.g., 14-2, 14-3 in FIG. 1 ). In this regard, a dielectric reflector 18 may be provided circumferentially surrounding the LED chip 36 and the first pattern trace 14 and on the region of the submount 12 that is not provided with the first pattern trace 14. The dielectric reflector 18 may even be positioned to extend to and contact the sidewall of the first pattern trace 14 adjacent to the LED chip 36. Thus, the cover structure mounting region includes the dielectric reflector 18 rather than the first pattern trace 14. As illustrated, the dielectric reflector 18 may include a thickness equal to or greater than that of the first pattern trace 14 to facilitate bonding of the cover structure 38. In other embodiments, dielectric reflector 18 may include a thickness that is less than the thickness of first pattern trace 14. In addition, portions of dielectric reflector 18 may be provided in gaps between discontinuous portions of first pattern trace 14 (e.g., 14-2, 14-3 in FIG. 1 ) that form die attach pads. To avoid topography differences for mounting LED chip 36, such portions of dielectric reflector 18 may have a thickness that is less than the thickness of first pattern trace 14.

[0052]

[0073] 12 is a cross-sectional view of an LED package 54 similar to the LED package 52 of FIG. 11 except that the dielectric reflector 18 is not located within the cover structure mounting area. As illustrated, first pattern traces 14 are provided in the area of ​​the submount 12 for the die attach pad and in the area of ​​the submount 12 for the cover structure mounting area. In this regard, the dielectric reflector 18 may cover the portion of the submount 12 within the cavity 40 that is not covered by the first pattern trace 14. In certain embodiments, the dielectric reflector 18 may be positioned to extend to and even contact the sidewalls of the first pattern trace 14 adjacent to the LED chip 36 and the cover structure mounting area.

[0053]

[0074] FIG. 13 is a cross-sectional view of an LED package 56 taken along a portion of the LED package 56 similar to section line AA in FIG. 1 , where the LED package 56 includes a reflector structure 58 disposed between the cover structure 38 and the submount 12. In certain embodiments, the reflector structure 58 is a separate element that may be mounted or otherwise attached to one or more of the first pattern trace 14 and the submount 12. As illustrated, the cover structure 38 may be attached to the reflector structure 58, and the reflector structure 58 and the cover structure 38 are attached to a cover structure mounting area provided around the LED chip 36. In FIG. 13 , the cover structure mounting area of ​​the submount 12 may be defined as where the reflector structure 58 is mounted to the first pattern trace 14. The reflector structure 58 may include an interior sidewall 58′ that defines a lateral boundary of the cavity 40. In certain embodiments, the sidewalls 58' may be angled relative to the submount 12 to redirect light emitted laterally from the LED chip 36 through the cover structure 38 to a desired light emission direction of the LED package 56. In other embodiments, the sidewalls 58' may form vertical sidewalls that are substantially perpendicular to the submount 12 while redirecting light emission laterally from the LED chip 36.

[0054]

[0075] The reflector structure 58 may include a material having a sufficient coefficient of thermal expansion (CTE) relative to the rest of the LED package 56. In certain embodiments, the reflector structure 58 may comprise silicon and optionally have a metal coating, for example, aluminum or its alloy, on the sidewalls 58′. In other embodiments, the entire reflector structure 58 may comprise a metal, such as aluminum or its alloy. In still other embodiments, the reflector structure 58 may comprise a ceramic, such as one or more of aluminum oxide (Al2O3), zirconium dioxide (ZrO2), silicon dioxide (SiO2), and aluminum nitride (AlN). For embodiments in which the reflector structure 58 comprises a ceramic material, the sidewalls 58′ may be coated with a metal, as described above, to enhance reflectivity. As illustrated, a dielectric reflector 18 is provided on the exposed portions of the first pattern traces 14 within the cavity 40 to enhance reflectivity. The dielectric reflector 18 may also be disposed on portions of the submount 12 below the LED chip 36 in the die attach area and / or between discontinuous portions of the first pattern traces 14, such as adjacent to the LED chip 36. Although the cover structure 38 is illustrated as planar in FIG. 13 , the cover structure 38 may form a dome- or hemispherical-shaped lens for directing light emitted from the LED chip 36.

[0055]

[0076] 14 is a cross-sectional view of an LED package 60 similar to the LED package 56 of FIG. 13 , in which the dielectric reflector 18 extends over the first pattern trace 14 at a location between the reflector structure 58 and the submount 12. At this point, the reflector structure 58 may be directly bonded to the dielectric layer 18. As illustrated, extending the dielectric reflector 18 over a portion of the first pattern trace 14 and the submount 12 may simplify manufacturing steps and may also provide electrical isolation between the reflector structure 58 and the dielectric reflector 18.

[0056]

[0077] 15 is a cross-sectional view of an LED package 62 similar to the LED package 56 of FIG. 13 , in which the dielectric reflector 18 extends along the sidewalls 58′ of the reflector structure 58. In this manner, the dielectric reflector 18 can cover the floor and sidewalls 58′ surrounding the cavity 40 to enhance reflectivity. In such an embodiment, the dielectric reflector 18 can be formed inside the LED package 62 after the reflector structure 58 is attached and before the LED chip 36 is provided. As with the other embodiments, the dielectric reflector 18 can be disposed on a portion of the submount 12 between discontinuous portions of the first pattern traces 14, such as below the LED chip 36 in the die attach region and / or adjacent to the LED chip 36.

[0057]

[0078] 16 is a cross-sectional view of an LED package 64 similar to the LED package 62 of FIG. 15 , in which the dielectric reflector 18 extends along the sidewall 58′ of the reflector structure 58, between the reflector structure 58 and the first pattern trace 14. In this manner, the first pattern trace 14 and a portion of the dielectric reflector 18 on the submount 12 may be formed before the reflector structure 58 is attached, and the portion of the dielectric reflector 18 on the sidewall 58′ may be formed after the reflector structure 58 is attached to the submount 12.

[0058]

[0079] It is contemplated that any of the foregoing aspects and / or various individual aspects and features described herein may be combined to further advantage. Any of the various embodiments disclosed herein may be combined with one or more of the other disclosed embodiments, unless indicated to the contrary herein.

[0059]

[0080] Those skilled in the art will recognize improvements and modifications to the preferred embodiments of the present disclosure, and all such improvements and modifications are considered to be within the scope of the concepts disclosed herein and the following claims.

Claims

1. 1. A light emitting diode (LED) package comprising: a submount having a first surface and a second surface opposite the first surface; at least one LED chip on the first surface of the submount; a cover structure disposed above the at least one LED chip; pattern traces on the first surface of the submount, the cover structure being attached to the pattern traces at a cover structure mounting area outside at least one die attach pad; a dielectric reflector on a portion of the pattern trace between the at least one die attach pad and the cover structure mounting area, the dielectric reflector comprising a distributed Bragg reflector; An LED package comprising:

2. 10. The LED package of claim 1, wherein the distributed Bragg reflector is a non-periodic distributed Bragg reflector.

3. the non-periodic distributed Bragg reflector comprises a plurality of dielectric layers; 3. The LED package of claim 2, wherein each dielectric layer of the plurality of dielectric layers has a unique optical thickness relative to other dielectric layers of the plurality of dielectric layers.

4. 4. The LED package of claim 3, wherein the plurality of dielectric layers comprises alternating dielectric layers of a first material type and a second material type.

5. 10. The LED package of claim 1, further comprising the dielectric reflector on a portion of the submount not covered by the pattern traces and the at least one LED chip.

6. 6. The LED package of claim 5, wherein the dielectric reflector is further disposed between the at least one LED chip and the submount in a gap formed by the pattern trace along the at least one die attach pad.

7. 7. The LED package of claim 6, wherein the at least one LED chip is configured to provide a peak wavelength in the range of 200 nm to 400 nm.

8. 1. A light emitting diode (LED) package comprising: a submount having a first surface and a second surface opposite the first surface; at least one LED chip on the first surface of the submount; a cover structure disposed above the at least one LED chip, the cover structure mounted to the submount at a cover structure mounting area spaced from a peripheral boundary of the at least one LED chip; a pattern trace on the first surface of the submount, the pattern trace forming at least one die attach pad for the at least one LED chip; a dielectric reflector on a portion of the submount laterally adjacent to the pattern traces, the dielectric reflector comprising a distributed Bragg reflector; An LED package comprising:

9. 10. The LED package of claim 8, wherein the dielectric reflector is further disposed on a portion of the pattern trace.

10. The LED package according to claim 8 , wherein the dielectric reflector is further disposed between the cover structure and the submount in the cover structure mounting region.

11. the distributed Bragg reflector is a non-periodic distributed Bragg reflector; the non-periodic distributed Bragg reflector comprises a plurality of dielectric layers; 10. The LED package of claim 8, wherein each dielectric layer of the plurality of dielectric layers has a unique optical thickness relative to other dielectric layers of the plurality of dielectric layers.

12. 12. The LED package of claim 11, wherein the plurality of dielectric layers comprises alternating dielectric layers of a first material type and a second material type.

13. 12. The LED package of claim 11, wherein the dielectric layer having the largest optical thickness among the plurality of dielectric layers is spaced apart from the top surface of the non-periodic distributed Bragg reflector and is located inside the non-periodic distributed Bragg reflector.

14. 10. The LED package of claim 8, wherein the at least one LED chip is configured to provide a peak wavelength in the range of 200 nm to 400 nm.

15. 1. A light emitting diode (LED) package comprising: a submount having a first surface and a second surface opposite the first surface; at least one LED chip on the first surface of the submount; a pattern trace on the first surface of the submount; a dielectric reflector on a portion of the pattern trace and on a portion of the submount laterally adjacent to the pattern trace, the dielectric reflector comprising a distributed Bragg reflector; An LED package comprising:

16. 16. The LED package of claim 15, wherein the distributed Bragg reflector is a non-periodic distributed Bragg reflector.

17. the non-periodic distributed Bragg reflector comprises a plurality of dielectric layers; 17. The LED package of claim 16, wherein each dielectric layer of the plurality of dielectric layers has a unique optical thickness relative to other dielectric layers of the plurality of dielectric layers.

18. 20. The LED package of claim 17, wherein the plurality of dielectric layers comprises alternating dielectric layers of a first material type and a second material type.

19. 18. The LED package of claim 17, wherein the dielectric layer having the largest optical thickness among the plurality of dielectric layers is spaced apart from the top surface of the non-periodic distributed Bragg reflector and is located inside the non-periodic distributed Bragg reflector.

20. the pattern trace comprises at least one die attach pad for the at least one LED chip; 16. The LED package of claim 15, wherein the dielectric reflector is further disposed between the at least one LED chip and the submount in a gap formed by the pattern trace along the at least one die attach pad.

21. 16. The LED package of claim 15, wherein the at least one LED chip is configured to provide a peak wavelength in the range of 200 nm to 400 nm.

22. 16. The LED package of claim 15, further comprising a cover structure disposed over the submount to form a cavity above the at least one LED chip.

23. 23. The LED package of claim 22, further comprising a reflector structure disposed between the cover structure and the submount, a sidewall of the reflector structure surrounding a portion of the cavity.

24. 24. The LED package of claim 23, wherein the dielectric reflector is disposed on the sidewalls of the reflector structure.

25. 24. The LED package of claim 23, wherein the dielectric reflector is disposed between the reflector structure and the submount.

Images