Arrangement of multi-junction LED chips in LED packaging and related displays

Abstract

Solid-state light-emitting devices are disclosed, and more specifically, arrangements of multi-junction light-emitting diode (LED) chips in LED packages and corresponding LED displays are disclosed. The multi-junction LED chips are arranged together with single-junction LED chips in the LED package. The multi-junction LED chips are configured to have the same or similar forward voltage as the single-junction LED chips in the same LED package. Common anode or common cathode arrangements for multi-junction and single-junction LED packages are disclosed. Multi-junction LED chips configured to provide an emission wavelength different from that of single-junction LED chips while having the same or similar forward voltage are disclosed.

Description

Technical Field

[0001] This disclosure relates to solid-state light-emitting devices, and more specifically, to the arrangement of multi-junction light-emitting diode (LED) chips in LED packages and related displays. Background Technology

[0002] Solid-state lighting 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, mechanically robust, and long-lasting light sources. Consequently, modern LEDs are widely used in various lighting scenarios, including backlighting for liquid crystal display (LCD) systems (e.g., as an alternative to cold cathode fluorescent lamps) and direct-view LED displays. Applications utilizing LED arrays also include vehicle headlights, street lighting, luminaires, and various indoor, outdoor, and special applications. Desired characteristics for LED devices include high luminous efficiency, long lifespan, and color gamut.

[0003] LEDs convert electrical energy into light and typically comprise one or more active layers (or active regions) of semiconductor material disposed between opposingly doped n-type and p-type layers. When a bias voltage is applied to the doped layers, holes and electrons are injected into the one or more active layers, where holes recombine with electrons to generate emission, such as visible light or ultraviolet light. Multicolor LED packages have been developed, comprising LED chips with different emission colors disposed within the same package structure. In some applications, LED chips may be disposed close to each other on a common base, which can increase the complexity of the corresponding electrical connections. As LED applications continue to evolve, there remains a challenge in providing high luminous emission efficiency while producing high-quality light with the desired emission characteristics.

[0004] The art continues to seek improved LED and solid-state lighting devices with desired lighting characteristics that overcome the challenges associated with conventional lighting devices. Summary of the Invention

[0005] This disclosure relates to solid-state light-emitting devices, and more specifically, to the arrangement of multi-junction light-emitting diode (LED) chips in LED packages and corresponding LED displays. The multi-junction LED chips are arranged together with single-junction LED chips in the LED package. The multi-junction LED chips are configured to have the same or similar forward voltage as the single-junction LED chips in the same LED package. Common anode or common cathode arrangements for multi-junction and single-junction LED packages are disclosed. Multi-junction LED chips configured to provide an emission wavelength different from that of the single-junction LED chips while having the same or similar forward voltage are disclosed.

[0006] In one aspect, an LED package includes: a support element; at least one single-junction LED chip on the support element, the at least one single-junction LED chip including a first forward voltage; and at least one multi-junction LED chip on the support element, the at least one multi-junction LED chip including at least two light-emitting junctions, the at least two light-emitting junctions being electrically coupled in series, and the at least one multi-junction LED chip including a second forward voltage within 25 percent of the first forward voltage. In some embodiments, the second forward voltage is within 15 percent of the first forward voltage. The LED package may further include a conductive element on the support element, the conductive element forming a common anode connection or a common cathode connection of the at least one single-junction LED chip and the at least one multi-junction LED chip. In some embodiments, the support element is a base having a plurality of patterned traces on its surface. In some embodiments, the support element is a lead frame structure including a lead frame and a housing, and the conductive element is a single lead of the lead frame. In some embodiments, the at least one single-junction LED chip and the at least one multi-junction LED chip are electrically coupled to the conductive element via wiring junctions. In some embodiments, at least one of at least one single-junction LED chip and at least one multi-junction LED chip is flip-chip mounted and electrically coupled to a conductive element. In some embodiments, the support element includes a lead frame structure, and at least one single-junction LED chip is electrically coupled to a pair of leads of the lead frame structure that are different from those of at least one multi-junction LED chip. In some embodiments: at least one single-junction LED chip is configured to emit light at a first peak wavelength; and at least one multi-junction LED chip is configured to emit light at a second peak wavelength, the second peak wavelength differing from the first peak wavelength by at least 20 nanometers (nm). The LED package may further include: an additional multi-junction LED chip configured to emit light at a third peak wavelength, the third peak wavelength differing from the first peak wavelength and the second peak wavelength by at least 20 nm; and an additional single-junction LED chip configured to emit light at a fourth peak wavelength, the fourth peak wavelength differing from the first peak wavelength, the second peak wavelength, and the third peak wavelength by at least 20 nm; wherein the additional multi-junction LED chip includes a third forward voltage, the third forward voltage being within 25 percent of the first forward voltage and the second forward voltage.

[0007] In another aspect, an LED package includes: a support element; at least one unijunction LED chip on the support element; at least one multijunction LED chip on the support element; and a conductive element on the support element, the conductive element forming a common anode connection or a common cathode connection between the at least one unijunction LED chip and the at least one multijunction LED chip. In some embodiments, the support element is a base, and the conductive element is a patterned trace on the surface of the base. In some embodiments, the support element is a lead frame structure including a lead frame and a housing, and the conductive element is a single lead of the lead frame. In some embodiments, the support element includes a lead frame structure, and at least one unijunction LED chip is electrically coupled to a pair of leads of the lead frame structure that are different from those of the at least one multijunction LED chip. In some embodiments, at least one of the at least one unijunction LED chip and at least one multijunction LED chip is electrically coupled to the conductive element via a wiring junction. In some embodiments, at least one of the at least one unijunction LED chip and at least one multijunction LED chip is flip-chip mounted and electrically coupled to the conductive element. In some embodiments: at least one single-junction LED chip is configured to emit light at a first peak wavelength; and at least one multi-junction LED chip is configured to emit light at a second peak wavelength, wherein the second peak wavelength differs from the first peak wavelength by at least 20 nanometers (nm). The LED package may further include: an additional multi-junction LED chip configured to emit light at a third peak wavelength, wherein the third peak wavelength differs from the first and second peak wavelengths by at least 20 nm; wherein conductive elements form a common anode connection or a common cathode connection between the single-junction LED chip, the multi-junction LED chip, and the additional multi-junction LED chip. The LED package may further include: an additional single-junction LED chip configured to emit light at a fourth peak wavelength, wherein the fourth peak wavelength differs from the first, second, and third peak wavelengths by at least 20 nm; wherein conductive elements form a common anode connection or a common cathode connection between the single-junction LED chip, the additional single-junction LED chip, the multi-junction LED chip, and the additional multi-junction LED chip.

[0008] In another aspect, an LED display includes: a display panel; and at least one LED package, the at least one LED package including: at least one unijunction LED chip; and at least one multijunction LED chip, the at least one unijunction LED chip and the at least one multijunction LED chip forming pixels of the display panel. In some embodiments, at least one of the at least one unijunction LED chip and the at least one multijunction LED chip is electrically coupled to a common anode connection or a common cathode connection. In some embodiments: the at least one unijunction LED chip includes a first forward voltage; and the at least one multijunction LED chip includes a second forward voltage, the second forward voltage being within 25 percent of the first forward voltage.

[0009] In another respect, any of the foregoing aspects (alone or together) and / or the individual aspects and features described herein may be combined to achieve additional advantages. Unless indicated to the contrary herein, any of the features and elements disclosed herein may be combined with one or more other disclosed features and elements.

[0010] Those skilled in the art, after reading the following detailed description of preferred embodiments in conjunction with the accompanying drawings, will understand the scope of this disclosure and realize its additional aspects. Attached Figure Description

[0011] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate various aspects of this disclosure and, together with the specification, serve to explain the principles of this disclosure.

[0012] Figure 1A This is a top view of a light-emitting diode (LED) package with a multi-junction LED chip having a forward voltage similar to that of one or more single-junction LED chips.

[0013] Figure 1B It is along Figure 1A The section line 1B-1B is cut off Figure 1A The cross-section of the LED package.

[0014] Figure 1C It is along Figure 1A The section line 1C-1C is cut off Figure 1A The cross-section of the LED package.

[0015] Figure 2A It is used for flip-chip implementation and Figures 1A to 1C A top view of an LED package similar to the one shown.

[0016] Figure 2B It is along Figure 2A The section line 2B-2B is cut off. Figure 2A The cross-section of the LED package.

[0017] Figure 2C It is along Figure 2A The section line 2C-2C is cut off Figure 2A The cross-section of the LED package.

[0018] Figure 3 This is for implementations that include additional multi-junction LED chips and additional single-junction LED chips. Figures 1A to 1C A top view of an LED package similar to the one shown.

[0019] Figure 4 This is for implementations that do not include common anode or common cathode connections. Figures 1A to 1C A top view of an LED package similar to the one shown.

[0020] Figure 5A This is a top view of an LED package, similar to an LED package, in which the supporting element for the LED package is a lead frame structure.

[0021] Figure 5B The LED chip has been omitted for illustrative purposes. Figure 5A Top 3D view of the LED package.

[0022] Figure 6A This is for implementations that do not include common anode or common cathode connections. Figure 5A and Figure 5B A top view of an LED package similar to the one shown.

[0023] Figure 6B The LED chip has been omitted for illustrative purposes. Figure 6A Top 3D view of the LED package.

[0024] Figure 7 This is a schematic diagram of an LED display (e.g., an indoor and / or outdoor screen) that includes an LED package according to the principles of this disclosure. Detailed Implementation

[0025] The embodiments described below illustrate the necessary information to enable those skilled in the art to practice these embodiments and explain the best mode for practicing these embodiments. After reading the following description with reference to the accompanying drawings, those skilled in the art will understand the concepts of this disclosure and recognize the application of these concepts not specifically mentioned herein. It should be understood that these concepts and applications fall within the scope of this disclosure and the appended claims.

[0026] It will be understood that while the terms first, second, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, without departing from the scope of this disclosure, a first element may be referred to as a second element, 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 associated listed items.

[0027] It will be understood that when an element (such as a layer, region, or substrate) is referred to as being "on" or extending "to" another element, it may be directly on or directly extending onto the other element, or an intermediary element may be present. In contrast, when an element is referred to as being "directly on" another element or "directly" extending "to" another element, no intermediary element is present. Similarly, it will be understood that when an element (such as a layer, region, or substrate) is referred to as being "above" or extending "above" another element, it may be directly on or directly extending over the other element, or an intermediary element may be present. In contrast, when an element is referred to as being "directly on" another element or extending "directly" on "above" another element, no intermediary element is present. It will also be understood that when an element is referred to as being "connected" or "coupled" to another element, it may be directly connected to or coupled to the other element, or an intermediary element may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, no intermediary 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 shown in the figures. It will be understood that these terms, and those discussed above, are intended to cover different orientations of the device 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 this disclosure. As used herein, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” are also intended to include the plural forms. It will also be understood that the terms “comprise,” “comprising,” “include,” and / or “including,” when used herein, specify the presence of the stated feature, integral, step, operation, element, and / or component, 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) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will also be understood that the terms used herein shall be interpreted as having the same meaning as they have in the context of this specification and the relevant field, and shall not be construed as having an idealized or overly formal meaning unless expressly defined herein.

[0031] Embodiments are described herein with reference to illustrative illustrations of embodiments of this disclosure. Therefore, the actual dimensions of layers and elements may differ, and variations in shape from the illustrations are contemplated due to, for example, manufacturing techniques and / or tolerances. For instance, areas shown 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 shown in the figures are schematic, and their shapes are not intended to show the precise shapes of the areas of the device, nor are they intended to limit the scope of this disclosure. Additionally, for illustrative purposes, the dimensions of structures or areas may be exaggerated relative to other structures or areas, and thus the dimensions of such structures or areas are provided to illustrate the general structure of the subject matter, and the dimensions of such structures or areas may or may not be drawn to scale. Common elements between figures may be shown herein using common element numbers and may not be described again subsequently.

[0032] This disclosure relates to solid-state light-emitting devices, and more specifically, to the arrangement of multi-junction light-emitting diode (LED) chips in LED packages and corresponding LED displays. The multi-junction LED chips are arranged together with single-junction LED chips in the LED package. The multi-junction LED chips are configured to have the same or similar forward voltage as the single-junction LED chips in the same LED package. Common anode or common cathode arrangements for multi-junction and single-junction LED packages are disclosed. Multi-junction LED chips configured to provide an emission wavelength different from that of the single-junction LED chips while having the same or similar forward voltage are disclosed.

[0033] Before delving into the specific details of the various aspects of this disclosure, an overview of various elements that may be included in the exemplary LED packages of this disclosure is provided for context. LED chips typically include active LED structures or regions that may have many different semiconductor layers arranged in different ways. The fabrication and operation of LEDs and their active structures are generally known in the art and are only briefly discussed herein. The layers of active LED structures can be fabricated using known processes, with metal-organic chemical vapor deposition being a suitable process. The layers of an active LED structure may include many different layers and typically include an active layer sandwiched between opposingly doped n-type and p-type epitaxial layers, all of which are formed continuously on a growth substrate. It should be understood that additional layers and elements may also be included in the active LED structure, including but not limited to buffer layers, nucleation layers, superlattice structures, undoped layers, cladding layers, contact layers, and current diffusion layers, as well as light extraction layers and elements. Active layers may include single quantum wells, multiple quantum wells, dual heterostructures, or superlattice structures.

[0034] Active LED structures can be fabricated from various material systems, some of which are group III nitride systems. Group III nitrides are semiconductor compounds formed between nitrogen (N) and elements in group III of the periodic table (typically aluminum (Al), 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 a common n-type dopant, and magnesium (Mg) is a common p-type dopant. Therefore, for group III nitride-based material systems, the active layer, n-type layer, and p-type layer can comprise one or more layers of GaN, AlGaN, InGaN, and AlInGaN, either undoped or doped with Si or Mg. Other material systems include organic semiconductors and other group III-V systems, such as gallium phosphide (GaP), gallium arsenide (GaAs), and related compounds. Active LED structures can be grown on a growth substrate, which can include many materials such as sapphire, silicon carbide (SiC), aluminum nitride (AlN), and GaN.

[0035] Different implementations of active LED structures can emit light of different wavelengths depending on the composition of the active layer and the n-type and p-type layers. In some implementations, the active LED structure emits blue light with a peak wavelength range of 430 nanometers (nm) to 480 nm. In other implementations, the active LED structure emits green light with a peak wavelength range of 500 nm to 570 nm. In other implementations, the active LED structure emits orange and / or red light with a peak wavelength range of 600 nm to 700 nm. In a further implementation, the active LED structure can emit cyan light with a peak wavelength range of 485 nm to 500 nm or violet light with a peak wavelength range of 400 nm to 420 nm. In some implementations, the active LED structure can be configured to emit light beyond the visible spectrum, including one or more portions of the ultraviolet (UV) spectrum, infrared (IR) spectrum, or near-IR spectrum. The UV spectrum is typically divided into three wavelength range categories denoted by the letters A, B, and C. In this manner, UV-A light is typically defined as having a peak wavelength range from 315 nm to 400 nm, UV-B as having a peak wavelength range from 280 nm to 315 nm, and UV-C as having a peak wavelength range from 100 nm to 280 nm. UV LEDs have attracted particular attention due to their use in applications related to the disinfection of microorganisms in air, water, and surfaces. In other applications, UV LEDs can also be provided with one or more fluorescent materials to provide LED packages with polymeric emission, which have a broad spectrum and improved color quality for visible light applications. The near-IR and / or IR wavelengths of the LED structures disclosed herein can have wavelengths above 700 nm, such as wavelengths ranging from 700 nm to 1000 nm or greater.

[0036] As used herein, a layer or region incident on a light-emitting device can be considered "transparent" when at least 80% of the emitted radiation is emitted through that layer or region. Additionally, as used herein, a layer or region incident on an LED is considered "reflective" or embodies a "mirror" or "reflector" when at least 80% of the emitted radiation is reflected. In some embodiments, the emitted radiation includes visible light, such as blue and / or green LEDs with or without fluorescent materials. In other embodiments, the emitted radiation can include invisible light. For example, in the case of GaN-based blue and / or green LEDs, silver (Ag) can be considered a reflective material (e.g., at least 80% reflection). In the case of UV LEDs, suitable materials can be selected to provide the desired, and in some embodiments, high reflectivity and / or the desired, and in some embodiments, low absorptivity. In some embodiments, a "light-transmitting" material can be configured to transmit at least 50% of the emitted radiation at the desired wavelength.

[0037] This disclosure applies to LED chips having various geometries, such as vertical or horizontal geometries. Vertical geometry LED chips typically include anode and cathode connections on opposite sides or faces of the LED chip. Horizontal geometry LED chips typically include 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 horizontal geometry LED chip can be mounted on a substrate of an LED package such that the anode and cathode connections are on the face of the LED chip opposite the substrate. In this configuration, wiring junctions can be used to provide electrical connections to the anode and cathode connections. In other embodiments, the horizontal geometry LED chip can be flip-chip mounted on the surface of a substrate of an LED package such that the anode and cathode connections are on the face of the active LED structure adjacent to the substrate. In this configuration, traces or patterns can be provided on the substrate to provide electrical connections to the anode and cathode connections of the LED chip. In a flip-chip configuration, the active LED structure is disposed between the substrate of the LED chip and the substrate of the LED package. Therefore, light emitted from the active LED structure can pass through the substrate in the desired emission direction. In other embodiments, the active LED structure can be bonded to a carrier substrate and the growth substrate can be removed so that light can leave the active LED structure without passing through the growth substrate.

[0038] According to aspects of this disclosure, a multi-chip LED package may include one or more elements, such as phosphor materials, sealants, light-modifying materials, lenses, and electrical contacts, which are disposed together with multiple LED chips. In some aspects, the LED package may include a support member, such as a base or lead frame. Suitable materials for the base 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 base 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 PCBs, metal-core PCBs, or any other type of PCB. In a further embodiment, the support structure may be embodied as a lead frame structure.

[0039] This disclosure relates to a monolithic LED chip in which multiple light-emitting junctions are formed on and supported by a common layer or substrate. In this manner, when multiple light-emitting junctions are arranged on the common layer or substrate of a single LED chip, the single LED chip can be referred to as a multi-junction LED chip. The multiple light-emitting junctions can be electrically isolated from each other while also being formed by a common LED epitaxial structure. Some embodiments include an overall electrical connection connecting the multiple light-emitting junctions in series. In some aspects, when present, the common layer can be provided by a common epitaxial layer continuous on the multiple light-emitting junctions. In some aspects, the common substrate can be provided by a common growth substrate on which an epitaxial structure is initially formed, wherein the common growth substrate is continuous on the multiple light-emitting junctions. An exemplary method for forming a multi-junction LED chip may include full-area epitaxial deposition of a continuous LED epitaxial structure at the wafer level, followed by electrical isolation of individual junctions within the LED epitaxial structure. Individual multi-junction LED chips can then be diced from the wafer. In this manner, at least one of the common layer and the common substrate can be retained in the individual multi-junction LED chip to provide mechanical support for each of the corresponding junctions.

[0040] The size or area of ​​the individual junctions in a multi-junction LED chip can be scaled to achieve desired emission intensity and distribution. In some embodiments, each junction may include a size ranging from a smaller size (such as 0.5 mm x 0.5 mm) to a larger size (such as 2 mm x 2 mm), or other sizes ranging from 0.5 mm x 0.5 mm to 1 mm x 1 mm. In some embodiments, the longest lateral dimension of each junction may range from 0.5 mm to 2 mm, or from 1 mm to 2 mm, or from 0.5 mm to 1 mm. Within at least one such range of 0.5 mm and larger, the different junctions of a multi-junction LED chip may be well-suited to providing high output power within a compact footprint. In some aspects, the spacing between the different junctions may be smaller than the possible spacing between the individual LED chips. In some embodiments, the width of the channels formed between the individual junctions may range from 20 micrometers (μm) to 200 μm, or from 20 μm to 100 μm. Such smaller channel widths can provide sharper contrast between adjacent junctions (especially when light alters the material), while also reducing any dark emission points created by larger conventional spacing. Larger channel widths are also possible depending on the desired application.

[0041] LED packages comprising multiple LED chips have been developed, which are aggregated together to provide increased light output and / or the ability of a single LED package to emit light of multiple colors and / or peak wavelengths. However, individually formed LED chips may have varying voltage requirements, especially for LED chips based on different material systems that emit different peak wavelengths. For example, blue and green emitting LED chips can be formed using gallium nitride-based materials and their alloys. Such blue and green LED chips typically have a forward voltage or turn-on voltage ranging from 2.7 volts (V) to 3.5 V. In contrast, red and yellow LED chips can be formed using gallium phosphide-based materials and / or gallium arsenide-based materials. Such red and yellow LED chips typically have a forward voltage ranging from 1.6 V to 1.8 V. Such variations can result in non-uniform light emission and / or complex electrical connections to accommodate the different voltage requirements. Complex circuitry and / or individual drivers are often required to accommodate different forward voltages within a common LED package. Furthermore, differences in forward voltage can generate heat and lead to associated power losses. Based on the human eye's response to color differences, red and / or yellow LED chips may also appear generally darker compared to blue and / or green LED chips.

[0042] According to aspects of this disclosure, an LED package includes at least one single-junction LED chip and at least one multi-junction LED chip, the at least one multi-junction LED chip having a forward voltage or turn-on voltage that is the same as or close to the forward voltage of the at least one single-junction LED chip. For example, the forward voltage of the multi-junction LED chip may be within 25%, or less, or 15%, or 10%, or 5%, or 1% of the forward voltage of the at least one single-junction LED chip within the same LED package. According to some aspects, the forward voltage value is current-dependent, and the difference between different types of LED chips may be greater at higher operating currents. In some embodiments, the above percentage values ​​of forward voltage between the multi-junction LED chip and the single-junction LED chip are provided under typical grading conditions and / or at higher operating currents. In some aspects, multiple junctions within the multi-junction LED chip are series-coupled to increase the effective forward voltage of the multi-junction LED chip. By providing a more closely matched forward voltage, the LED package can be formed with reduced electrical connection complexity, and all LED chips can be driven by the same driver. In addition, more uniform emission from LED chips of different colors can be achieved using a more closely matched forward voltage.

[0043] Figure 1A This is a top view of an LED package 10 having a multi-junction LED chip 12 with a forward voltage similar to that of one or more single-junction LED chips 14-1, 14-2. The multi-junction LED chip 12 and the single-junction LED chips 14-1, 14-2 are mounted on a common support element 16. In the context of the LED package 10, the support element 16 is shown as the base of the LED package 10. In other embodiments, the described principles also apply when the support element 16 forms a lead frame structure with a lead frame and a corresponding housing. For the base embodiment, conductive elements in the form of a pattern of conductive traces 18-1 to 18-4 are provided on the top surface of the support element 16. The conductive traces 18-1 to 18-4 can be formed as patterned traces to provide electrical connections to the multi-junction LED chip 12 and the single-junction LED chips 14-1, 14-2.

[0044] As described above, different material systems used for LED emission at different wavelengths may have different forward voltage values. For example, LED chip 14-1 can be configured to emit a blue wavelength, and LED chip 14-2 can be configured to emit a green wavelength, both having forward voltages ranging from 2.7 V to 3.5 V. To enable LED package 10 to emit various colors together within a large color gamut, red and / or yellow wavelengths are required. For example, multi-junction LED chip 12 and single-junction LED chips 14-1 to 14-2 can both be configured to emit unique peak wavelengths at least 20 nm apart from each other. As described above, material systems used for such emission wavelengths provide significantly different forward voltages, such as forward voltages ranging from 1.6 V to 1.8 V. Figure 1A In this configuration, the multi-junction LED chip 12 is configured to emit a red wavelength, and the multi-junction LED chip 12 is further subdivided into two LED junctions 12 connected in series. J1 and 12 J2 By connecting two LEDs 12 J1 and 12 J2 In series coupling, the forward voltage of the multi-junction LED chip 12 can be effectively doubled to more closely match the forward voltage of the single-junction LED chips 14-1 and 14-2. For example, if two LED junctions 12 J1 and 12 J2 Each of the LED chips has a forward voltage of 1.7 V, so the multi-junction LED chip 12 can now have a total forward voltage of 3.4 V.

[0045] By more closely matching the forward voltage, the multi-junction LED chip 12 may not require separate electrical considerations, such as separate drivers and associated electrical connections. In this way, the multi-junction LED chip 12 and the single-junction LED chips 14-1, 14-2 can be electrically coupled to a single conductive element forming a common anode or common cathode connection, such as... Figure 1A Conductive trace 18-1 in the circuit. The anode or cathode of each of the multi-junction LED chip 12 and the single-junction LED chips 14-1, 14-2 can be coupled to different traces in traces 18-2 to 18-4 to provide individual addressability. In this respect, the multi-junction LED chip 12 can be individually controlled by the same driver used to individually control the single-junction LED chips 14-1, 14-2. In some embodiments, the multi-junction LED chip 12 and the single-junction LED chips 14-1, 14-2 can be electrically coupled to conductive traces 18-1 to 18-4 via wiring junction 20.

[0046] Figure 1B It is along Figure 1A The cross-section of the LED package 10 is taken by section line 1B-1B. In this respect, Figure 1BMulti-junction LED chip 12 and corresponding LED junction 12 are provided. J1 and 12 J2 The overall cross-section. LED junction 12 J1 and 12 J2 On the same side of substrate 22, and substrate 22 is mounted to support element 16 of LED package 10. In some embodiments, LED junction 12 is formed thereon on substrate 22. J1 and 12 J2 The growth substrate. For example, an epitaxial structure including an n-type layer 24, a p-type layer 26, and an active layer 28 therebetween can be epitaxially grown, and then subdivided into LED junctions 12. J1 and 12 J2 In this respect, each LED junction has 12 J1 and 12 J2 This includes individual portions of the same n-type layer 24, p-type layer 26, and active layer 28. In LED junction 12 J1 and 12 J2 A channel 30 is formed between the layers, and a passivation layer 32 may reside within the channel 30 to provide electrical isolation. A metal contact 34 may extend at least partially through the passivation layer 32 and even onto the top surface of the passivation layer to connect the LED junction 12. J1 The n-type layer 24 is electrically coupled to the LED junction 12. J2 The p-type layer 26. In this way, the LED junction 12 J1 and 12 J2 The LED junction 12 is electrically coupled in series within the multi-junction LED chip 12. J1 The first bonding pad 36-1 on the p-type layer 26 and the LED junction 12 J2 The second bonding pad 36-2 on the n-type layer 24 provides a contact point for the wiring joint 20.

[0047] In comparison, Figure 1C It is along Figure 1A The cross-section of the LED package 10 is taken by section line 1C-1C. In this respect, Figure 1C A general cross-section of a single-junction LED chip 14-1 is provided. The single-junction LED chip 14-1 includes a substrate 38, an n-type layer 40, a p-type layer 42, and an active layer 44 between the n-type layer 40 and the p-type layer 42. In this manner, the LED chip 14-1 has a single LED junction 14-1. J1 LED junction 14-1 J1 The first bonding pad 46-1 on the p-type layer 42 and the second bonding pad 46-2 on the n-type layer 40 provide contact points for the wiring joint 20.

[0048] refer to Figures 1A to 1C 14-1 single LED junction J1 ( Figure 1C The second bonding pad 46-2 and LED junction 12 J2 ( Figure 1B The second bonding pad 36-2 is coupled to the same conductive trace 18-1. Figure 1A To provide individual addressability, a single LED junction 14-1 J1 ( Figure 1C The first bonding pad 46-1 and LED junction 12 J1 ( Figure 1B The first bonding pad 36-1 is coupled to conductive traces 18-2 to 18-4. Figure 1A Different traces in ).

[0049] Figure 2A It is used for flip-chip implementation and Figures 1A to 1C A top view of an LED package 48 similar to the LED package 10. In this manner, one or more of the multi-junction LED chip 12 and the single-junction LED chips 14-1, 14-2 may include a flip-chip configuration electrically coupled to conductive traces 18-1 to 18-5 without the use of wiring junctions. As shown, portions of conductive traces 18-1 to 18-5 extend below corresponding portions of the multi-junction LED chip 12 and the single-junction LED chips 14-1, 14-2.

[0050] Figure 2B It is along Figure 2A The cross-section of the LED package 48 is taken from section line 2B-2B. In this respect, Figure 2B The support element 16 provides a flip-chip arrangement of multi-junction LED chips 12 and corresponding LED junctions 12. J1 and 12 J2 The overall cross-section. In this respect, the LED junction 12 J1 The p-type layer 26 is mounted and electrically coupled to the conductive trace 18-2, and the LED junction 12 J2 The n-type layer 24 is electrically coupled to the conductive trace 18-1. In some embodiments, an interconnect 50 is formed to provide a conductive path through the passivation layer 32 between the conductive trace 18-1 and the n-type layer 24. Conductive trace 18-5 is provided on the support element 16 to facilitate the LED junction 12. J1 and 12 J2 The series coupling. In this way, conductive trace 18-5 can be coupled to LED junction 12. J1 n-type layer 24 and LED junction 12 J2 Between the p-type layers 26. Another interconnect 50 can be provided through the passivation layer 32 to form a conductive path between the n-type layer 24 and the conductive traces 18-5.

[0051] In comparison, Figure 2C It is along Figure 2A The cross-section of the LED package 48 is taken from the cross-section line 2C-2C. In this respect, Figure 2C The overall cross-section of the single-junction LED chip 14-1 in the flip-chip arrangement on the support element 16 is provided.

[0052] refer to Figures 2A to 2C 14-1 single LED junction J1 ( Figure 2C n-type layer 40 and LED junction 12 J2 ( Figure 2B The n-type layer 24 is flip-chip mounted and electrically coupled to the same conductive trace 18-1. To provide individual addressability, a single LED junction 14-1... J1 ( Figure 2C p-type layer 42 and LED junction 12 J1 ( Figure 2B The p-type layer 26 is flip-chip mounted and electrically coupled to conductive traces 18-2 to 18-4. Figure 2A Different traces in ).

[0053] Figure 3 This is for embodiments that include an additional second multi-junction LED chip 54 and additional single-junction LED chips 14-1 to 14-4. Figures 1A to 1C The LED package 10 is a top view similar to the LED package 52. By adding additional LED chips, the LED package 10 can include the ability to emit additional wavelengths, which increases the color gamut of the aggregated emission. Exemplary additional wavelengths include yellow, cyan, amber, additional blue wavelengths (such as longer wavelengths of blue), and / or additional red wavelengths (such as longer wavelengths of red). Furthermore, the multi-junction LED chips 12, 54 and the single-junction LED chips 14-1 to 14-4 can be configured to have the same or similar forward voltages regardless of the emitted color, to provide the ability to drive all chips with a common LED driver. For example, each of the multi-junction LED chips 12, 54 and the single-junction LED chips 14-1 to 14-4 can have forward voltages that differ from each other by no more than 10% or 5%. In this way, each of the multi-junction LED chips 12, 54 and the single-junction LED chips 14-1 to 14-4 can be electrically coupled to the same conductive trace 18-1 for common anode or common cathode configurations. In some implementations, each of the multi-junction LED chips 12, 54 and the single-junction LED chips 14-1 to 14-4 can be configured to emit unique peak wavelengths that are at least 20 nm apart from each other.

[0054] Figure 4 This is for implementations that do not include common anode or common cathode connections. Figures 1A to 1CA top view of an LED package 56 similar to the LED package 10. As shown, the multi-junction LED chip 12 is electrically coupled between conductive traces 18-1 and 18-2, the unijunction LED chip 14-1 is electrically coupled between conductive traces 18-4 and 18-6, and the unijunction LED chip 14-2 is electrically coupled between conductive traces 18-3 and 18-5. Therefore, the multi-junction LED chip 12 and the unijunction LED chips 14-1 and 14-2 can be individually addressable without a common anode or common cathode configuration.

[0055] As indicated above, the principles of this disclosure are equally applicable to LED packages where the support element is embodied in a leadframe structure. A leadframe structure typically includes a leadframe with multiple metal leads and a housing. The leads are embedded within the housing, and the LED chip is electrically coupled to a portion of the leads accessible within an opening or recess in the LED package. Other portions of the leads may extend outside the housing to receive external electrical connections. In this manner, the principles of this disclosure (including...) Figures 1A to 4 (All diagrams) are applicable to lead frame structures where conductive traces are replaced with lead frames.

[0056] Figure 5A This is a top view of an LED package 58, which is similar to the LED package 10, and is an embodiment of a lead frame structure for the support element used in the LED package 58. Figure 5B The LED chip has been omitted for illustrative purposes. Figure 5A The image shows a top perspective view of the LED package 58. The LED package 58 is a leadframe package, comprising a leadframe structure formed by leads 60-1 to 60-4 within a housing 62. Multi-junction LED chips 12 and single-junction LED chips 14-1 and 14-2 reside in the recess 62 of the housing 62. R Inside, and is installed and / or electrically coupled to leads 60-1 to 60-4 in recess 62 R The exposed portion at the bottom or base. Figure 5A In the middle, the wiring joint is connected in a manner similar to Figure 1A The manner shown; however, as Figure 2A The flip-chip arrangement shown also applies. Using the same or similar forward voltage, each of the multi-junction LED chip 12 and the single-junction LED chips 14-1, 14-2 can be coupled to a common lead 60-1 for common anode or common cathode configurations. Figure 5B This is the perspective from which LED package 58 is led out from common lead 60-1.

[0057] Figure 6A This is for implementations that do not include common anode or common cathode connections. Figure 5A and Figure 5B A top view of LED package 58, similar to LED package 64. Figure 6BThe LED chip has been omitted for illustrative purposes. Figure 6A The top perspective view of the LED package 64. For the LED package 64, additional leads 60-5 and 60-6 are provided such that each of the multi-junction LED chip 12 and the single-junction LED chips 14-1, 14-2 is coupled to a different pair of leads 60-1 to 60-6.

[0058] Any implementation of this disclosure (including) Figures 1A to 6B LEDs are well-suited for deployment in LED display applications. Each LED package, containing a combination of one or more multi-junction LED chips and one or more single-junction LED chips, can be arranged as LED pixels in such applications. The same or similar forward voltage, as described herein, allows for more uniform emission from such LED displays while reducing the complexity of the LED driver.

[0059] Figure 7 This is a schematic diagram of a portion of an LED display screen 68 (e.g., an indoor and / or outdoor screen). Generally, the LED display screen includes a display panel comprising a driver printed circuit board (PCB) 70 carrying a large number of surface mount devices (SMDs) 72 arranged in rows and columns, each SMD 72 defining a pixel. The SMDs 72 may include, according to the specifications herein... Figures 1A to 6B The LED package described in any of the embodiments. The SMD 72 is electrically connected to traces or pads on the PCB 70 to respond to appropriate electrical signal processing and driver circuitry (not shown). It should be understood that, although Figure 7 The multi-junction LED chip 12 and single-junction LED chips 14-1, 14-2 are depicted in a linear arrangement, but in other embodiments, the multi-junction LED chip 12 and single-junction LED chips 14-1, 14-2 can be arranged in different layouts.

[0060] It is anticipated that any of the foregoing aspects and / or the individual aspects and features described herein can be combined to achieve additional advantages. Any of the various embodiments disclosed herein may be combined with one or more other disclosed embodiments, unless indicated to the contrary herein.

[0061] Those skilled in the art will recognize improvements and modifications to the preferred embodiments of this disclosure. All such improvements and modifications are considered to be within the scope of the concepts disclosed herein and the appended claims.

Claims

1. A light-emitting diode (LED) package, comprising: Supporting elements; At least one single-junction LED chip, on the supporting element, the at least one single-junction LED chip includes a first forward voltage; as well as At least one multi-junction LED chip, on the supporting element, the at least one multi-junction LED chip includes at least two light-emitting junctions, the at least two light-emitting junctions are electrically coupled in series, and the at least one multi-junction LED chip includes a second forward voltage, the second forward voltage being within 25 percent of the first forward voltage.

2. The LED package according to claim 1, wherein, The second forward voltage is less than 15 percent of the first forward voltage.

3. The LED package according to claim 1 further includes a conductive element on the support element, wherein the conductive element forms a common anode connection or a common cathode connection between the at least one single-junction LED chip and the at least one multi-junction LED chip.

4. The LED package according to claim 3, wherein, The support element is a base with multiple patterned traces on its surface.

5. The LED package according to claim 3, wherein, The support element is a lead frame structure comprising a lead frame and a housing, and the conductive element is a single lead of the lead frame.

6. The LED package according to claim 3, wherein, The at least one single-junction LED chip and the at least one multi-junction LED chip are electrically coupled to the conductive element through a wiring junction.

7. The LED package according to claim 3, wherein, At least one of the at least one single-junction LED chip and the at least one multi-junction LED chip is flip-chip mounted and electrically coupled to the conductive element.

8. The LED package according to claim 1, wherein, The support element includes a lead frame structure, and the at least one single-junction LED chip is electrically coupled to a pair of leads of the lead frame structure that are different from those of the at least one multi-junction LED chip.

9. The LED package according to claim 1, wherein: The at least one single-junction LED chip is configured to emit light with a first peak wavelength; and The at least one multi-junction LED chip is configured to emit light at a second peak wavelength, and the second peak wavelength differs from the first peak wavelength by at least 20 nanometers (nm).

10. The LED package according to claim 9, further comprising: An additional multi-junction LED chip is configured to emit light at a third peak wavelength, which differs from the first and second peak wavelengths by at least 20 nm. as well as An additional single-junction LED chip is configured to emit light at a fourth peak wavelength, which differs from the first, second, and third peak wavelengths by at least 20 nm. The additional multi-junction LED chip includes a third forward voltage, which is within 25 percent of the first forward voltage and the second forward voltage.

11. A light-emitting diode (LED) package, comprising: Supporting elements; At least one single-junction LED chip is on the support element; At least one multi-junction LED chip is on the support element; as well as A conductive element is provided on the supporting element, wherein the conductive element forms a common anode connection or a common cathode connection for the at least one single-junction LED chip and the at least one multi-junction LED chip.

12. The LED package according to claim 11, wherein, The supporting element is a base, and the conductive element is a patterned trace on the surface of the base.

13. The LED package according to claim 11, wherein, The support element is a lead frame structure comprising a lead frame and a housing, and the conductive element is a single lead of the lead frame.

14. The LED package according to claim 11, wherein, The support element includes a lead frame structure, and the at least one single-junction LED chip is electrically coupled to a pair of leads of the lead frame structure that are different from those of the at least one multi-junction LED chip.

15. The LED package according to claim 11, wherein, At least one of the at least one single-junction LED chip and the at least one multi-junction LED chip is electrically coupled to the conductive element through a wiring junction.

16. The LED package according to claim 11, wherein, At least one of the at least one single-junction LED chip and the at least one multi-junction LED chip is flip-chip mounted and electrically coupled to the conductive element.

17. The LED package according to claim 11, wherein: The at least one single-junction LED chip is configured to emit light with a first peak wavelength; and The at least one multi-junction LED chip is configured to emit light at a second peak wavelength, and the second peak wavelength differs from the first peak wavelength by at least 20 nanometers (nm).

18. The LED package according to claim 17, further comprising: An additional multi-junction LED chip is configured to emit light at a third peak wavelength, which differs from the first and second peak wavelengths by at least 20 nm. The conductive element is formed by the single-junction LED chip, the multi-junction LED chip, and the additional multi-junction LED chip to form the common anode connection or the common cathode connection.

19. The LED package according to claim 18, further comprising: An additional single-junction LED chip is configured to emit light at a fourth peak wavelength, which differs from the first, second, and third peak wavelengths by at least 20 nm. The conductive element is formed by the single-junction LED chip, the additional single-junction LED chip, the multi-junction LED chip, and the additional multi-junction LED chip to form the common anode connection or the common cathode connection.

20. A light-emitting diode (LED) display, comprising: Display panel; as well as At least one LED package, comprising: At least one single-junction LED chip; as well as At least one multi-junction LED chip, wherein the at least one single-junction LED chip and the at least one multi-junction LED chip form pixels of the display panel.

21. The LED display according to claim 20, wherein, At least one of the at least one single-junction LED chip and the at least one multi-junction LED chip is electrically coupled to a common anode connection or a common cathode connection.

22. The LED display according to claim 20, wherein: The at least one single-junction LED chip includes a first forward voltage; and The at least one multi-junction LED chip includes a second forward voltage, which is within 25 percent of the first forward voltage.

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