LED array and method for fabricating same

A light emitting device or array comprising a submount having a top surface, a bottom surface and a plurality of edges, with input and output terminals disposed on the top surface. A plurality of attach pads and traces are also disposed on the top surface and electrically connected between the input and output terminals. A plurality of LEDs are also included, each of which is mounted to one of the attach pads. The attach pads cover more of the top surface than the LEDs and spread heat from the LEDs to the top surface of the submount. A plurality of lenses are also included each of which is molded over a respective one of the attach pads and covers the LED mounted to the particular attach pad. The arrays are shaped and arranged so that they can be easily attached to similar arrays in a tiling fashion, with the desired number of arrays included to meet the desired lighting requirements. Methods for fabricating the arrays from a single submount or submounts panel are also disclosed.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to lighting systems, and more particularly to interconnected light emitting diode (LED) arrays.

Description of the Related Art

LEDs are semiconductor photon sources that can serve as highly efficient electronic-to-photonic transducers. They are typically forward-biased p-n junctions fabricated from a semiconductor material that emits light via injection electroluminescence. Their small size, high efficiency, high reliability, and compatibility with electronic systems make them very useful for a multitude of applications. Recent advancements have yielded high-power LEDs in a range of colors. This new generation of LEDs is useful in applications requiring a higher intensity light output such as high-power flash lights, airplane lighting systems, fiber-optic communication systems, and optical data storage systems.

High-flux lighting solutions are required by various modern applications such as street lighting, airport/airplane lighting systems, pool lighting systems, and many others. In order to achieve additional luminous output, multiple LEDs are often arranged in various configurations or arrays. These arrays may take nearly any shape and usually include several individual LEDs.

In order to further increase luminous output, several LED arrays may be grouped together on a surface. Providing the necessary electrical connections to power the LED arrays can be challenging. The layout of the individual LEDs on the array surface determines where the input and output connections must be located on the surface and how the LED arrays must be arranged so that they can be connected together.

As the number of LED arrays that are grouped together increases, the circuitry needed to connect the arrays can become complex and expensive. The circuit topology required to power the arrays often requires circuit elements that cannot be mounted on the surface of the arrays. This can result in circuit elements that obscure the light emitters and prevent the light from escaping to the outside environment, greatly decreasing the efficiency of the arrays.

SUMMARY OF THE INVENTION

One embodiment of an emitter array according to the present invention comprises a submount having a plurality of edges, with input and output terminals and a plurality of attach pads on the submount. A plurality of solid state emitters is included, with at least one of each mounted on and electrically connected to each of the attach pads. The attach pads cover more of the submount than the emitters and laterally spread heat from the emitters to the surface of the submount. Electrical connections are also included that connect the emitters and attach pads with the input and output terminals. A plurality of lenses are also included each of which is molded over a respective one of the attach pads and each of which covers the emitters attached to the respective one of the attach pads.

One embodiment of an LED array according to the present invention comprises a submount having a top surface, a bottom surface and a plurality of edges. Input and output terminals are disposed on the top surface, and a plurality of electrically and thermally conductive elements are on the top surface. A plurality of LEDs is attached to the conductive elements, so that an electrical signal applied to the conductive elements causes the LEDs to emit light. At least some of the conductive elements also spread heat from the LEDs across the top surface. A plurality of lenses is included each of which is molded over a respective one of the electrical elements.

One embodiment of a lamp according to the present invention comprises a lamp body having an opening and a light source arranged within the body to radiate light out of the body through the opening. The light source comprising a plurality of arrays arranged in an expandable tiling on a surface, and a network of conductors connected to provide power to the arrays. Each of the arrays comprises an input and an output terminal on a submount with the terminals connected to the network. A plurality of top electrically and thermally conductive elements is included on a surface of the submount, and a plurality of LEDs is included at least one of which is attached to the top elements with power from the network causing the LEDs to emit light. The top elements also spread heat from the LEDs across the submount top surface. A plurality of lenses is also included each of which is molded to the submount over at least one of the LEDs.

One embodiment of a method for fabricating an array according to the present invention comprises providing a submount and forming sets of electrically conductive features on one surface of the submount. A plurality of LEDs are attached to the electrically conductive features such that the LEDs are electrically connected by the plurality of conductive features. The conductive features are sized to spread heat from the LEDs into at least a portion of the submount. A plurality of lenses are molded on the submount with each of the lenses over one of the LEDs. Alternative methods can also be used to fabricate a plurality of arrays from a submount panel, including the step of singulating the panel to separate the individual arrays from the panel.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to compact, simple and efficient light emitting devices or arrays and methods for manufacturing same. Each array can comprise a submount with a plurality of LEDs coupled together to emit light simultaneously when an electrical signal is applied to the array. The arrays according to the present invention can include features to provide for improved thermal management including spreading heat from the LED into the submount from where the heat can then dissipate into a heat sink attached at the bottom of device or the ambient. This allows the arrays to operate under higher power and emit higher luminous flux without overheating.

The submounts of the arrays are shaped so that multiple arrays can be mounted closely together and electrically connected to form a light source wherein all the arrays emit light in response to an electrical signal. Depending on the requirements for the particular application, different numbers of arrays can be coupled together. Arrays according to the present invention can also comprise lenses molded directly over their LEDs to protect the LED while still allowing for efficient emission characteristics. Secondary optics can also be included over the lenses to further shape or disperse the LED light. The present invention is also directed to methods for fabricating arrays that generally comprise molding lenses directly over the LEDs on the arrays.

It is understood that when an element such as a layer, region or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. Furthermore, relative terms such as “inner”, “outer”, “upper”, “above”, “lower”, “beneath”, and “below”, and similar terms, may be used herein to describe a relationship of one layer or another region. It is understood that these terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures.

Embodiments of the invention are described herein with reference to cross-sectional view illustrations that are schematic illustrations of idealized embodiments of the invention. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances are expected. Embodiments of the invention should not be construed as limited to the particular shapes of the regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. A region illustrated or described as square or rectangular will typically have rounded or curved features due to normal manufacturing tolerances. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region of a device and are not intended to limit the scope of the invention.

The present invention can be used with many different solid state emitters with the embodiments of the invention below being described in relation to LEDs, and in particular to white emitting LEDs. The lighting devices or arrays utilizing the white emitting LEDs provide a white emitting light source. It is understood however that different LEDs emitting at different colors can also be used, so that the array emits the color from its LEDS. It is also understood that different colors of LEDs can be used in a single array to generate the desired color of light. For example, red emitting LEDs can be combined with white emitting LEDs so that the array emits a warm white light. The present invention can also be used in many different applications and the discussion of the present invention with reference to the following embodiment should not be construed as limiting to the that particular embodiment or similar embodiments.

FIG. 1ashows one embodiment of a light emitting device or array100according to the present invention. Light emitting array100can serve as an array element when linking several of the devices together to increase luminescent output. Substrate/submount102comprises top surface104and a bottom surface (not shown). Various electronic and optical components can be mounted to top surface104including at least one light emitting element106. In many embodiments a plurality of light emitting elements106are included on the submount102. Such components may include vertical cavity surface emitting lasers (VCSELs), light emitting diodes (LEDs), or other semiconductor devices. In one embodiment the element106comprises an LED.

LED structures and their fabrication and operation are generally known in the art and only briefly discussed herein. The layers of an LED can be fabricated using known processes with a suitable process being fabrication using metal organic chemical vapor deposition (MOCVD). The layers of LEDs generally comprise an active layer/region sandwiched between first and second oppositely doped epitaxial layers all of which are formed successively on a growth substrate. LEDs can be formed on a wafer and then singulated for mounting in a package. It is understood that the growth substrate can remain as part of the final singulated LED or the growth substrate can be fully or partially removed.

It is also understood that additional layers and elements can also be included in the LED, including but not limited to buffer, nucleation, contact and current spreading layers as well as light extraction layers and elements. The active region can comprise single quantum well (SQW), multiple quantum well (MQW), double heterostructure or super lattice structures. The active region and doped layers may be fabricated from different material systems, with preferred material systems being Group-III nitride based material systems. Group-III nitrides refer to those semiconductor compounds formed between nitrogen and the elements in the Group III of the periodic table, usually aluminum (Al), gallium (Ga), and indium (In). The term also refers to ternary and quaternary compounds such as aluminum gallium nitride (AlGaN) and aluminum indium gallium nitride (AlInGaN). In a preferred embodiment, the doped layers are gallium nitride (GaN) and the active region is InGaN. In alternative embodiments the doped layers may be AlGaN, aluminum gallium arsenide (AlGaAs) or aluminum gallium indium arsenide phosphide (AlGaInAsP).

The growth substrate can be made of many materials such at sapphire, silicon carbide, aluminum nitride (AlN), GaN, with a suitable substrate being a 4H polytype of silicon carbide, although other silicon carbide polytypes can also be used including 3C, 6H and 15R polytypes. Silicon carbide has certain advantages, such as a closer crystal lattice match to Group III nitrides than sapphire and results in Group III nitride films of higher quality. Silicon carbide also has a very high thermal conductivity so that the total output power of Group-III nitride devices on silicon carbide are typically not limited by the thermal dissipation of the substrate (as may be the case with some devices formed on sapphire). SiC substrates are available from Cree Research, Inc., of Durham, N.C. and methods for producing them are set forth in the scientific literature as well as in a U.S. Pat. Nos. Re. 34,861; 4,946,547; and 5,200,022.

The LED can also comprise a conductive current spreading structure and one or more wire bond pads on its top surface, both of which are made of a conductive material and can be deposited using known methods. Some materials that can be used for these elements include Au, Cu, Ni, In, Al, Ag or combinations thereof and conducting oxides and transparent conducting oxides. The current spreading structure generally comprises conductive fingers arranged in a grid on the LED with the fingers spaced to enhance current spreading from the pads into the LED's top surface. In operation, an electrical signal is applied to the pads through a wire bond as described below, and the electrical signal spreads through the fingers of the current spreading structure and the top surface into the LED. Current spreading structures are often used in LEDs where the top surface is p-type, but can also be used for n-type materials.

The LED can be coated with one or more phosphors with the phosphors absorbing at least some of the LED light and emitting a different wavelength of light such that the LED emits a combination of light from the LED and the phosphor. In a preferred embodiment the LED emits a white light combination of LED and phosphor light. The LED can be coated using many different methods, with one suitable method being described in U.S. patent application Ser. Nos. 11/656,759 and 11/899,790, both entitled “Wafer Level Phosphor Coating Method and Devices Fabricated Utilizing Method”, and both of which are incorporated herein by reference. Alternatively the LEDs can be coated using other methods such as electrophoretic deposition (EPD), with a suitable EPD method described in U.S. patent application Ser. No. 11/473,089 entitled “Close Loop Electrophoretic Deposition of Semiconductor Devices”, which is also incorporated herein by reference. It is understood that LED packages according to the present invention can also have multiple LEDs of different colors, one or more of which may be white emitting.

The light emitting elements106are mounted to top surface104and are shown connected in series via conductive features or traces108which is disposed on top surface104. The traces108can be made of different conductive materials such as metals. The light emitting elements106can also be connected in a parallel configuration or in a combination of series and parallel connections. Input terminal110is located near the edge of submount102. Output terminal112is located near the opposite edges of submount102across from input terminal110. Current from a power source (not shown) flows from input terminal110through light emitting elements106to output terminal112, illuminating the array100.

Submount102can have many different shapes with a preferred shape being a regular hexagon. However, submount102may also be shaped as a regular polygon such as a square, a pentagon, etc. Submount102may also be shaped as an irregular polygon. Submount102as shown inFIG. 1ais a regular hexagon having six edges of equal length. In this embodiment, input terminal110is disposed along three adjacent edges. Input terminal110comprises three input contact pads114, each of which is located near to a corresponding one of the three input-side edges. Output terminal112comprises three output contact pads116which are located near the three adjacent edges on the output-side, opposite the input terminal110.

The input and output contact pads114,116are disposed on top surface104along the edges to provide easy access to the input and output terminals110,112. This allows for flexibility when designing an array layout to connect several light emitting array elements.

Several light emitting elements106may be mounted to top surface104and can be arranged in many different configurations on top surface104. The light emitting elements can be connected in parallel, in series, or in a combination of both to achieve optimal light output. A preferred pattern comprises seven light emitting elements106arranged in a serial serpentine pattern as shown inFIG. 1a. Current flows from input contact pad114through all of the light emitting elements106to output contact pad116.

Bore holes118are disposed near opposite vertices between the outer input and output contact pads114,116. Bore holes118are used to facilitate mounting the devices to a surface. They can be sized to accommodate a variety of screws or mounting pins.

FIG. 1bis a side front view of a light emitting array100according to one embodiment of the present invention. Light emitting array100has a top surface104and a bottom surface132. Lighting elements106are mounted to top surface and electrically connected.

Because lighting elements106can generate large amounts of heat, it may be necessary to channel that heat away from lighting elements106and other circuit elements that might be damaged by the heat. One method to dissipate the excess heat that is generated into the ambient atmosphere is to incorporate a heat spreader into the device. There are several designs which can be used to achieve thermal dissipation.FIG. 1billustrates one such design. Heat spreader134has a high thermal conductivity over a broad range of temperatures and is disposed beneath top surface104. Heat spreader134may be made from copper, aluminum and ceramic, for example; although it could also be made from any high thermal conductivity material. In the design shown inFIG. 1b, heat spreader134forms the bottom surface132of the device.

The embodiment of light emitting array100as illustrated inFIG. 1bis oriented such that input terminal110(not visible in this view) is on the left-hand side of the figure as indicated by the positive sign (+). Likewise the output terminal112(not visible in this view) is on the right-hand as indicated by the negative sign (−). In this embodiment viewed from this orientation, an output contact pad116(not visible in this view) is disposed near the front edge.

Bore holes136are shown with dashed lines to indicate that they are set off a distance from the front edge of array100. The holes136pass through top and bottom surfaces104,132, allowing array100to be easily mounted to other surfaces. As mentioned above, devices100can be mounted to a surface in several different ways including but not limited to methods using screws, epoxy adhesives and solders.

FIG. 2is a top plan view of a light source150according to the present invention having three light emitting devices or arrays152,154,156according to one embodiment of the present invention. Devices152,154,156are connected in a serial arrangement. The arrows indicate the direction of current flow through the devices. Current flows into152at one of the edges marked with a positive (+). The current then flows through the light emitters (not shown), out of device152at one of the edges marked with a negative sign (−), and into one of the positive edges of device154. Device156is shown positioned adjacent to the middle negative edge of device154.

However, device156can also be disposed in either of two alternate positions158(shown with hashed lines). Because the positive and negative terminals are easily accessible from multiple sides of each device, there is a great deal of flexibility in designing the layout of the devices in an array and the path through which current will flow. The layout ofFIG. 2is just one simple example of an array of devices and is meant to illustrate the additional freedom of design afforded by various embodiments of the invention. One skilled in the art will recognize that the devices can be easily rotated, shifted and expanded to achieve a desired layout and current flow. An example of such an array is described below and illustrated inFIG. 3.

FIG. 3is a top plan view of an array170of light emitting devices100according to one embodiment of the present invention. Devices100function as array elements and are arranged in a tiling which can be expanded in all directions to accommodate luminescent output requirements. Devices100are oriented such that edges of the respective devices that face each other are parallel. Spacing between the devices100can vary according to design specifications, for example, to accommodate different types of conductors. In this embodiment the devices100are mounted on a flat surface.

In the orientation shown inFIG. 3, current from a power source (not shown) enters the array at the upper left-hand corner as indicated by the positive sign (+). Current then travels from the input terminals through the light elements to the output terminals in each array element. The output terminals are connected to the input terminals of adjacent array elements via conductors (not shown). According to this embodiment, current travels through the array elements in a serpentine pattern. The direction of current flow is shown as indicated by the arrows. However, there are many possible array layouts that may be employed to achieve design goals.

Because the input and output terminals are accessible from three sides in this particular embodiment, the design engineer has a great deal of flexibility in arranging the array elements. The array can be expanded in any direction, allowing for various circuit connection schemes and increasing output efficiency.

Other embodiments may utilize array elements having different shapes such as squares, pentagons, or octagons, for example. Combinations of such shapes may also be used to develop a specific array layout.

FIG. 4is a perspective view of a three-dimensional (3-D) array180of light emitting devices184according to one embodiment of the present invention. Devices184may be mounted to the surface of a 3-D structure182to achieve omnidirectional luminescence. This particular embodiment comprises hexagonal and pentagonal array elements184that correspond to the substantially spherical 3-D structure182on which the devices184are mounted.

In this embodiment the structure182is mounted on a support186. Current may be delivered from a power source (not shown) either external to the structure182or from within the structure182or the support186. This particular embodiment illustrates a power source external to the structure182. Current flows through some or all of the array elements184and back out of the structure182as shown by the polarity arrows.

Alternate embodiments may include structures having any 3-D shape. Array elements that are mounted to those structures may also come in any shape in order to efficiently cover part or all of the surface of the structure.

FIGS. 5athrough 5fshow another embodiment of a light emitting device or array200comprising a substrate/submount202having a top surface204and bottom surface206. The substrate/submount can be made of many different structures and materials such as a printed circuit board (PCB), metal core printed circuit board (MCPCB). Other suitable materials include, but are not limited to ceramic materials such as aluminum oxide, aluminum nitride or organic insulators like polyimide(PI) and polyphthalamide(PPA) laminated with thermally and electrically conductive materials such as copper or other similar materials. In other embodiments the submount202can comprise a printed circuit board (PCB), sapphire or silicon or any other suitable material, such as T-Clad thermal clad insulated substrate material, available from The Bergquist Company of Chanhassen, Minn. For PCB embodiments different PCB types can be used such as standard FR-4 PCB, metal core PCB, or any other type of printed circuit board.

As more fully described below, arrays according to the present invention can be fabricated using a method that utilizes a submount panel sized to accommodate a plurality of arrays. Multiple arrays can be formed on the panel, with the individual arrays being singulated from the panel. In other embodiments the arrays can be fabricated from separate submounts instead of a panel of submounts.

As best shown inFIGS. 5aand 5b, the submount's top surface204comprises patterned conductive features208that can include a plurality of die attach pads210and interconnecting conductive traces212. Referring toFIGS. 5aand 5cthrough 5f, a plurality of LEDs214are provided that can be the same as the LEDs described above with reference to element106inFIGS. 1 and 2. Each of the LEDs214are mounted to a respective one of the attach pads, with each approximately at the center of its pad210. It is understood that in alternative embodiments multiple LEDs can be mounted to each of the respective one of the attached pads, with the LEDs emitting the same or different colors of light. Each of the LEDs can be electrically interconnected in a combination of serial and/or parallel connections. For example, the LEDs on at least some of the attach pads can be connected in parallel, such that the array comprises a serial connection between the pads with the attach pads having a parallel connection.

The patterned conductive features208provide conductive paths for electrical connection to the LEDs214using known contacting methods. The LEDs can be mounted to the attach pads210using known methods and materials such as using conventional solder materials that may or may not contain a flux material, or dispensed polymeric materials that may be thermally and electrically conductive.

The attach pads210and traces212can comprise different materials such as metals or other conductive materials. In one embodiment the pads210and traces212can comprise copper deposited using known techniques such as plating. In typical plating processes a titanium adhesion layer and copper seed layer are sequentially sputtered onto a substrate. Then, approximately 75 microns of copper is plated onto the copper seed layer. The resulting copper layer being deposited can then be patterned using standard lithographic processes. In other embodiments the layer can be sputtered using a mask to form the desired pattern.

In some embodiments according to the present invention some of the conductive features208can include only copper, with others of the features including additional materials. For example, the attach pads210can be plated or coated with additional metals or materials to the make each more suitable for mounting LEDs214. In one such embodiment the attach pads210can be plated with adhesive or bonding materials, or reflective and barrier layers. A wire bond (not shown) can be included between each LED214and an adjacent one of the traces212such that all the LEDs are connected in series between the pads210and the traces212. Other methods to connect the LEDs on the attach pad210with the traces212can comprise a flip-chip bonded LED with co-planar metal contacts (e.g. stud bumps) on the LED providing the connection between the attach pad210, the traces212, and the LED diode contacts.

The conductive features208can also comprise input and output contact pads216,218, that can be made of the same materials and deposited in the same way as the other conductive features. The contact pads216,218are typically on opposing sides of the submount with the input contact pad216coupled to a trace212leading to the first in the series of attach pads210, and the output contact pad218coupled to the last in the series attach pads. With the LEDs214mounted in place on the their attach pads210and electrically connected to the traces212, a signal applied to the input contact pad216conducts through each of the LEDs214, attach pads210and interconnecting traces212, to the output contact pad218. The signal could then be transmitted to another similar array200using known jumper methods.

To improve heat dissipation in the array200from the LEDs214, the attach pads210can provide thermally conductive paths to conduct heat away from the LEDs214such that heat can spread to other areas of the submount beyond the areas just below the LEDs214. The attach pads210cover more of the surface of the top surface204than the LEDs214, with the attach pads extending from the edges of the LEDs214. In the embodiment shown, each of the attach pads210are generally circular and extend radially from its respective one of the LEDs214. It is understood that the contact pads216,218can be many other shapes and in some embodiments it can extend further on the submount's top surface to improve thermal dissipation of heat generated in the LED214.

In embodiments where the submount202comprises a metal core printed circuit board, adequate levels of heat can spread from the attach pads210through the submount202. In embodiments where the submount comprises a material that is less thermally conductive, such as a ceramic, additional elements can be included to further assist in heat dissipation. In one such embodiment, the submount's bottom surface206can comprise a separate thermal pad or sets of thermal pads that can be in vertical alignment with the attach pads on the top surface. The bottom thermal pads serve to dissipate heat or conduct heat to heat sink from where head is dissipated into the ambient.

Although heat from the LEDs214is spread over the top surface204of the submount202by the attach pads210more heat will pass into the submount202directly below and around the LEDs214. The metalized area can assist with this dissipation by allowing this heat to spread into the metalized area where it can dissipate more readily. The metalized layer can be made of known thermally conductive materials, such as metals, deposited using known techniques.

In other embodiments the array can be arranged for surface mounting by having surface mount contacts (not shown) on the submount's bottom surface206. The input and output contact pads216,218can also be connected to the submount bottom surface using electrically conductive via connections. By providing the corresponding set of pads on the bottom surface of the submount, the arrays can be interconnected by using known printed circuit board and surface mount technology. The surface mount contacts are arranged to be compatible with surface mount processes, and can be in electrical contact with the conductive features on the submount's top surface204. In one embodiment conductive vias can be included through the submount to provide this electrical connection.

An optical elements or lenses220are formed on the submount's top surface204, with each of the lenses being over a respective one of the LEDs214to provide both environmental and/or mechanical protection. The lenses220can be in different locations on the top surface204with the lenses located as shown with their respective one of the LEDs214at approximately the center of the lens base. In some embodiments each or some of the lenses220can be formed in direct contact with one of the LEDs214and the submount's top surface204. In other embodiments there may be an intervening material or layer between the LED220and/or top surface204. Direct contact to the LED214provides certain advantages such as improved light extraction and ease of fabricating.

As further described below, the lenses220can be molded over the LEDs214using different molding techniques and the lens can be many different shapes depending on the desired shape of the light output. One suitable shape as shown is hemispheric, with some examples of alternative shapes being ellipsoid bullet, flat, hex-shaped and square. Many different materials can be used for the lens such as silicones, plastics, epoxies or glass, with a suitable material being compatible with molding processes. Silicone is suitable for molding and provides suitable optical transmission properties. It can also withstand subsequent reflow processes and does not significantly degrade over time. It is understood that one or more of the lenses220can also be textured to improve light extraction or can contain materials such as phosphors or scattering particles.

In other embodiments, the array can also comprise a protective layer (not shown) covering the submount's top surface204not covered by the lenses220. The protective layer can provide additional protection to the elements on the top surface204to reduce damage and contamination during subsequent processing steps and use. The protective layer can be formed during formation of the lenses220and can comprise the same material as the lenses220. Openings should be formed in the protective layer to provide access to the first and second contact pads216,218, with the openings formed using known processes.

As best shown inFIGS. 5dthrough 5f, the arrangement of the lenses220is also easily adapted for use with secondary optics222that can be included over the lenses during fabrication of the array200or by the end user. The optics222can be included for different purposes such as to facilitate beam shaping or beam dispersion. Secondary optics are generally known in the art, with many of them being commercially available. They can be formed from many different materials such as plastics (PMMA, PC) and can be formed from processes such as injection molding. In other embodiments the lenses can be made of glass and can also be formed using known methods. The optics222can be integrated into a single assembly (as shown) that mounts as one piece over the lenses220, or in other embodiments the optics can comprise individual pieces, each of which is mounted over a respective one of the lenses220. The optics222can be mounted over the lenses using known mounting and bonding techniques.

The array200also comprises registration thru-holes224arranged to assist in aligning the secondary optics222to the array200during mounting of the optics. Lockdown thru-holes226are also included for mounting the array200in place for use, such as to a heat sink in a lamp.

The array200can also comprise elements to protect against damage from electrostatic discharge (ESD). These elements (not shown) can be mounted to the submount202, and different elements can be used such as various vertical silicon (Si) Zener diodes, different LEDs arranged in parallel and reverse biased to the LEDs, surface mount varistors and lateral Si diodes.

As best shown inFIG. 5c, a solder mask236can be included on the submount's top surface204, at least partially over the attach pads210and the first and second contact pads216,218, and covering the traces212. The solder mask236protects these features during subsequent processing steps and in particular mounting the LEDs214to the attach pads210and wire bonding. During these steps there can be a danger of solder or other materials depositing in undesired areas, which can result in damage to the areas or result in electrical shorting. The solder mask serves as an insulating and protective material that can reduce or prevent these dangers. It may also serve to promote the adhesion of the lenses to the submount surface204. The solder mask comprises opening for mounting the LEDs214to the attach pads210and for attaching wire bonds to the traces212. It also comprises side openings on the contact pads216,218for connecting jumpers between adjacent arrays.

FIGS. 6aand 6bshow another embodiment of an array250according to the present invention having a submount252similar to the submount102shown inFIGS. 1-3and described above, but also comprises molded lenses. The submount252has a top surface254having electrically conductive features256comprising die attach pads258, interconnecting traces260. LEDs261are mounted to the attach pads258as described above and electrically connected to their adjacent traces260, so that the LEDs are connected in series or in parallel (not shown). The attach pads258are arranged to extend on the top surface of the submount252to facilitate lateral heat spreading from the LEDs261, and to allow the heat to spread into the submount where it can dissipate.

First and second contact pads262,264are arranged on the top surface254to provide access to each of the pads262,264from three edges of the submount252. This provides flexibility in connecting several luminaries in an array.

The array250further comprises lenses266and secondary optics268similar to the lenses220and secondary optics222described above in conjunction withFIGS. 5athrough 5f. The array250can also comprise lock down thru holes for mounting by the end user, such as in a lamp.

Contact pads262,264are around three edges of the submount252, which leaves less area for the attach pads around the edges. Accordingly, for these embodiments the attach pads can be located closer to the center of the submount compared to those embodiments not having contacts around the edges.

Arrays according to the present invention can be arranged in many different ways from the arrays100,200,250described above, and can be include different elements or components beyond those described above. In some embodiments electrical drive circuits or electrical conditioning circuits can be included on the array either as discrete or integrated components. The arrays can also comprise other elements to enhance heat spreading such as heat fins or various heat sinks. Accordingly, the present invention should not be construed as limited to the embodiments shown and described.

As described above, the arrays can be connected together for use in many different applications.FIG. 7shows one embodiment of a light source300comprising luminaries302that are similar to those described above and shown inFIGS. 5athrough 5f. Jumpers (not shown) can be included between contact pads of adjacent arrays302, so that an electrical signal applied the first of the arrays302is conducted to the others. The interconnected arrays302are preferably mounted to a surface304that can also serve as a heat sink to draw heat away from the arrays.

The light source300can be used in many different lighting applications, with one being the light source for a lamp.FIG. 8shows one embodiment of a lamp350that can use the light source300and other array based light sources. The light source300is arranged within the lamp housing352so that light emits out through the housing opening354. The opening354can have a cover to protect the light source300or an opening optical element to both protect the light source and shape the emitting light. It is also noted that the housing352can have heat dissipating fins356to help dissipate the heat from the light source300.

The light source300can be arranged to emit many different colors of light with different intensities. Different LEDs can be used on the arrays302for different colors and temperatures of light. In one embodiment the light source can emit 1000 lumens or more. In embodiments having LEDs emitting cool white light, the light source300emits at 4000 to 10,000 correlated color temperature (CCT). In embodiments where the arrays have LEDs emitting warm white light, the light source300emits at 2700 to 4000K CCT. The white light source can also have a color rendering index of 80 or greater. The lamp350can also be provided with an integrated power supply that allows it to operate with an efficiency of 90 lumens per Watt or greater.

The present invention also provides for methods of fabricating arrays andFIG. 9shows one embodiment of an LED package fabrication method400according to the present invention. In402a substrate (submount) is provided that can have many different shapes but is preferably hexagon shaped, and sized to serve as the submount for a single array. Alternatively, a submount panel can be provided sized so that it can be diced in subsequent manufacturing steps to provide a plurality of individual submounts. This allows for simultaneous fabrication of a plurality of packages. It is understood that a separate processing step is required for providing the conductive features either for the individual submount or for the panel. These features can include the attach pad, traces, contact pads and metalized are, some of which can be arranged to assist in dissipating heat generated by the LED as described above. The panel comprises a plurality of these features arranged in sets, each of the sets corresponding to one of the plurality of arrays to be formed from the panel.

In404a plurality of LEDs are provided each of which is to be die attached to a respective one of the attach pads. In one embodiment, the plurality of LEDs comprise white emitting LEDs chips, and many different white chips can be used with a suitable white chip being described in the patent applications mentioned above and incorporated herein. In other embodiments more than one LED can be provided for mounting to each of the attach pads. In this step a plurality of ESD protection elements can also be provided, each of which can be mounted in conjunction with one of the attach pads to provide ESD protection for the LEDs. Many different mounting methods and materials can be used, such as mounting using conventional solder materials and methods. In this step each of the ESD elements can also be mounted to a respective attach pad using the same mounting method and material. It is understood that the ESD element can also be mounted in other locations using other methods.

In406electrical connections are formed between each of the LEDs on the attach pads and one of the adjacent traces so that the LEDs are connected in series between the attach pads. In this step the ESD element can also be connected to the respective trace. Wire bond connections can be formed using known processes and can be made of known conductive materials such as gold. It is understood that flip-chip bonded LED or ESD elements with co-planar contacts to their respective electrodes can also be used as an alternative method for connecting the devices to the traces. Other methods include eutectic attach and solder attach processes.

In some embodiments the LEDs can be provided and mounted to the panel without the desired white light conversion material. In these embodiments the conversion material can be deposited on the LED after wire bonding. In optional408the conversion material or phosphor is deposited on the LED, and many different known phosphor deposition methods can be used such as electrophoretic deposition (EPD), with a suitable EPD process described in the patent application mentioned above.

In410the first encapsulant is formed over the LEDs by molding over each of the LEDs and many different molding methods can be used. In one embodiment a molding process is used that simultaneously forms lenses over the LEDs submount (or submount panel). One such molding process is referred to as compression molding processes wherein a mold is provided having a plurality of cavities each of which has an inverted shape of the lens. Each cavity is arranged to align with a respective one of the LEDs on a submount. The mold is loaded with a lens material in liquid form filling the cavities, with the preferred material being liquid curable silicone. The submount is inverted and moved toward the cavity with each of the LEDs being embedded in the liquid silicone within one a respective one of the cavities. In one embodiment a layer of silicone can also remain between adjacent lenses that provides a protective layer over the top surface of the submount. The liquid silicone can then be cured using known curing processes. The submount can then be removed from the mold and the submount can comprise a plurality of molded lenses, each of which is over a respective one of the LEDs.

It is understood that other methods can be used for forming lenses according to the present invention. In one alternative method, the lenses can be formed over the LEDs using known dispensing processing and then cured.

For those embodiments of the method400utilizing a submount panel, optional412can be utilized to singulate the submount panel into individual arrays. In optional414an optical element can be mounted over the lenses in the form of secondary optics. These optics can be made of the materials described above, can be fabricated using the methods described above, and can be mounted over the lenses using known methods and materials. In416each of the arrays can be tested to be sure they are operating correctly and to measure each device output light characteristics. In418the LED packages can be shipped to the customer.

In embodiments where the submounts are provided in a panel, the panel can be diced/singulated to separate the individual arrays and different methods can be used such as known saw singulation methods. When using this method a tape can be attached to the panel prior to singulation to hold and stabilize the panel and individual arrays. Following singulation, the arrays can be cleaned and dried.

Although the present invention has been described in detail with reference to certain preferred configurations thereof, other versions are possible. Therefore, the spirit and scope of the invention should not be limited to the versions described above.