CN103907401B - Solid state light emitting device and method of forming - Google Patents

Abstract

A solid state light emitting apparatus can include a substrate having first and second opposing surfaces, wherein at least one of the opposing surfaces is configured to mount a device thereon. Strings of chip-on-board Light Emitting Diode (LED) groups may be located on the first surface of the substrate and connected in series with each other. An ac voltage source input from outside the solid state light emitting device can be coupled to the first surface or the second surface of the substrate.

Description

Solid state light emitting device and method of forming

CROSS-REFERENCE AND PRIORITY CLAIM TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 61/581,923, filed December 30, 2011, and it is co-deposited on July 28, 2011, titled Solid State Lighting Apparatus and Methods Using Integrated Driver Circuitry U.S. Patent Application Serial No. 13/192,755 (Attorney Docket: 5308-1364), U.S. Patent Application Serial No. 13/235,103, filed September 16, 2011, entitled Solid State Lighting Apparatus and Methods Using Energy Storage (Attorney Docket No. 5308-1459) and U.S. Patent Application Serial No. 13/235,127, entitled Solid State Lighting Apparatus and Methods Using Current Diversion Controlled By Lighting Device Bias States, filed September 16, 2011 (Attorney Docket: 5308-1461) Continuation-in-part of, claiming priority from, and related to, the entire disclosure of which is hereby incorporated by reference.

technical field

The subject matter of the present invention relates to light emitting devices and methods, and more particularly, to solid state light emitting devices and methods of forming.

Background technique

Solid state lighting arrays are used in many lighting applications. For example, solid state light emitting panels comprising arrays of solid state light emitting devices have been used as direct lighting sources, such as in architectural and/or accent lighting. Solid state light emitting devices can include, for example, packaged light emitting devices including one or more light emitting diodes (LEDs), which can include inorganic LEDs, which can include semiconductor layers forming a p-n junction, and/or organic LEDs (OLEDs), which can Including organic light-emitting layer.

Solid state lighting arrays are used in many lighting applications. For example, solid state light emitting panels comprising arrays of solid state light emitting devices have been used as direct lighting sources, such as in architectural and/or accent lighting. Solid state light emitting devices can include, for example, packaged light emitting devices including one or more light emitting diodes (LEDs). Typically inorganic LEDs include semiconductor layers forming a p-n junction. Organic LEDs (OLEDs), which include an organic light-emitting layer, are another type of solid-state light-emitting device. Typically, solid-state light-emitting devices generate light by recombining electron carriers, ie, electrons and holes, in the light-emitting layer or region.

Solid-state light-emitting panels are commonly used as backlights for small liquid crystal display (LCD) screens, such as those used in portable electronic devices. Additionally, the use of solid state light emitting panels as backlights has received increased attention for larger displays such as LCD television displays.

Although solid-state light sources have proven to have high color rendering index (CRI) and/or high efficiency, one problem with the mass adoption of such light sources in architectural applications is that commercial lighting systems employ lamps that are designed to run on alternating current (ac) power The standard connector, can use phase-cut dimmer equipment phase cut. Typically, solid-state light sources are powered by or connected to a power converter that converts AC power to DC power that is used to power the light source. However, use of such power converters may increase the cost of the light source and/or the overall installation, and may reduce efficiency.

Some attempts at powering solid state light sources have involved driving LEDs or strings or groups of LEDs using a rectified AC waveform. However, because LEDs require some minimum forward voltage to turn on, the LEDs may only turn on for a portion of the rectified AC waveform, which may cause visible flicker, may undesirably reduce the power factor of the system, and/or may increase the power factor of the system. resistive losses in the .

Other attempts to power AC-driven solid-state light sources have involved placing the LEDs in an anti-parallel configuration, so half the LEDs are driven for each half-cycle of the AC waveform. However, this approach requires twice as many LEDs to produce the same luminous flux as using a rectified AC signal.

Contents of the invention

A solid state light emitting device can include a substrate having first and second opposing surfaces, wherein at least one of the opposing surfaces is configured to mount a device thereon. Strings of chip-on-board (COB) light emitting diode (LED) groups may be located on the first surface of the substrate and connected in series with each other. An AC voltage source input from outside the solid state light emitting device may be coupled to either the first surface or the second surface of the substrate.

In some embodiments according to the invention, a solid state lighting device can include a rectifier circuit mounted on a surface of a substrate housed in the solid state lighting device, coupled to a An AC voltage source that provides a rectified AC voltage. A current source circuit may be mounted on the surface of the substrate and coupled to the rectifier circuit. Strings of groups of light emitting diodes (LEDs) may be mounted on the surface of the substrate and connected in series with each other and coupled to the current source circuit. A plurality of current shunt circuits can be mounted on the surface of the substrate, wherein respective current shunt circuits are coupled to respective nodes of the strings and can be configured to respond to a bias state of a respective one of the groups of LEDs Transform and operate.

In some embodiments according to the invention at least said plurality of current shunt circuits comprise discrete electronic component packages capable of being mounted on said substrate. In some embodiments according to the invention, the LEDs in the string may be chip-on-board LEDs mounted on the surface of the substrate. In some embodiments according to the invention, the substrate may be a flexible circuit substrate, wherein the device may further include a heat sink capable of being mounted on opposing surfaces of the substrate and thermally coupled to to the string of LED groups. In some embodiments according to the invention, the substrate can be a metal matrix printed circuit board (MCPCB).

In some embodiments according to the invention, a solid state lighting device can include a rectifier circuit that can be configured to be coupled to an AC power source to provide a rectified AC voltage. A current source circuit may be coupled to the rectifier circuit and a string of series-connected LED groups may be coupled to an output of the current source circuit. At least one capacitor may be coupled to the output of the current source circuit. The current limiter circuit can include a current mirror circuit configured to limit current through at least one of said LED groups to be less than a current produced by said current source circuit, responsive to The rectified AC voltage at the input of the circuit causes said at least one capacitor to be selectively charged via said current source circuit and discharged via at least one of said LED groups. A plurality of current shunt circuits can be coupled to respective nodes between the LEDs in the string and configured to be selectively enabled in response to a bias state transition of the group of LEDs as the magnitude of the rectified AC voltage varies. and disabled.

In some embodiments according to the invention, each of said plurality of current shunt circuits can comprise a transistor capable of providing a controllable current flow between the first node of said string and a terminal of said rectifier circuit A path and a shutdown circuit coupled to the second node of the string and the control terminal of the transistor and can be configured to control the current path in response to a control input.

In some embodiments according to the present invention, the device can further include a substrate having first and second opposing surfaces, wherein at least the string of series-connected LED groups, the plurality of current shunt circuits, the rectifier circuit, and The current source circuit is mounted on the substrate. In some embodiments according to the invention, the LEDs in the string may be chip-on-board LEDs mounted on the substrate.

In some embodiments according to the present invention, the substrate may be a flexible circuit board, wherein the device can further include a heat sink that can be opposed to and closely mounted on the string of LED groups. on the base. In some embodiments according to the invention, the substrate can be a metal matrix printed circuit board (MCPCB).

In some embodiments according to the present invention, methods of forming solid state lighting circuits can be provided by placing a plurality of chip-on-board light emitting diodes (LEDs) in a string configuration on a surface of a substrate. An encapsulant material can be applied over the plurality of chip-on-board LEDs and the encapsulant material can be formed as a layer covering the plurality of chip-on-board LEDs to provide a lens for the plurality of chip-on-board LEDs.

In some embodiments according to the invention, the method can further include placing a plurality of current shunt circuits, including discrete electronic component packages, on the surface of the substrate. In some embodiments according to the invention, applying the encapsulant material can be provided by applying the encapsulant material to cover the plurality of chip-on-board LEDs and surface portions between several of the plurality of chip-on-board LEDs.

In some embodiments according to the invention, the lens is provided for the plurality of chip-on-board LEDs by contacting a mold with the encapsulant material to simultaneously form a layer covering the plurality of chip-on-board LEDs It can be provided that said encapsulant material is formed into a layer, wherein said mold comprises chip-on-board LED recesses in a surface of said mold opposite said plurality of chip-on-board LEDs.

In some embodiments according to the invention, the method can further include placing a plurality of current shunt circuits, including discrete electronic component packages, on the surface of the substrate prior to applying the encapsulant material. Wherein the mold further includes discrete electronic component packaging recesses in a surface of the mold opposite the plurality of current shunt circuits on the surface. In some embodiments according to the invention, applying the encapsulant material can be provided by dispensing the encapsulant material separately onto the plurality of chip-on-board LEDs.

In some embodiments according to the invention, applying the encapsulant material can be provided by dispensing the encapsulant material onto the plurality of chip-on-board LEDs simultaneously. In some embodiments according to the invention, the encapsulant material is formed as a layer covering the plurality of chip-on-board LEDs to provide a lens for the plurality of chip-on-board LEDs, which can be achieved by applying the encapsulant material to A respective encapsulant barrier is provided during which the encapsulant material exits each of the plurality of chip-on-board LEDs.

In some embodiments according to the invention, the encapsulant barrier at least partially surrounds the LED and is configured to reduce flow of the encapsulant material away from the LED during application of the encapsulant material to facilitate the Lens formation. In some embodiments according to the invention, the method can further comprise removing the sealant barrier from the lens.

In some embodiments according to the invention, a printed circuit board (PCB) can include a substrate configured to include a solid state light emitting device, wherein the substrate can have first and second opposing surfaces, wherein at least one opposing surface is configured for mounting thereon a plurality of chip-on-board light-emitting diodes (LEDs), and the substrate is configured to be coupled to an AC voltage source input from outside the solid state lighting device and configured to mount thereon a plurality of discrete a current shunt circuit device coupled to respective nodes between the several LEDs and configured to respond to varying the bias state of the group of LEDs as a function of the magnitude of the rectified AC voltage supplied to the LEDs transitions to selectively enable and disable.

In some embodiments according to the invention, the substrate may be a metal-based PCB. In some embodiments according to the present invention, the first surface may be a conductive circuit pattern layer and the second surface may be a base metal layer having a thickness greater than the conductive circuit pattern layer, wherein the PCB can further include An insulating layer between the conductive circuit pattern layer and the base metal layer. In some embodiments according to the invention, the substrate can be a flexible PCB.

In some embodiments according to the present invention, the PCB can further include a thermally conductive fillet in the substrate at a specific position opposite to a position on which the string of chip-on-board LED sets is to be mounted. In some embodiments according to the present invention, said PCB can further comprise an encapsulant barrier protruding from said surface at least partially surrounding a location on said surface where at least one said LED is to be mounted , configured to reduce flow of the encapsulant material away from the LEDs during application of the encapsulant material to facilitate formation of the lens over at least one of the LEDs.

Description of drawings

1 is a schematic block diagram illustrating a solid state lighting device including a light emitting diode (LED) driver circuit and an LED string circuit in accordance with some embodiments of the present invention;

FIG. 2 is a schematic block diagram illustrating an LED drive circuit including the rectifier circuit and the current shunt circuit shown in FIG. 1 and an LED string circuit connected thereto in some embodiments according to the present invention;

3 is a schematic block diagram illustrating the LED driving circuit shown in FIGS. 1 and 2 in some embodiments according to the present invention, further including a current limiter circuit and a capacitor coupled to the LED string circuit;

4A is a plan view of an exemplary circuit substrate, including rectifier circuitry, LED string circuitry, and other discrete electronic component packaging on the substrate in a solid state light emitting device, in some embodiments according to the invention;

4B is a cross-sectional view of the exemplary circuit substrate shown in FIG. 4A, in accordance with some embodiments of the present invention;

4C is an alternative cross-sectional view of the LED string circuit portion of the exemplary circuit substrate shown in FIGS. 4A and 4B including a flexible circuit substrate in some embodiments in accordance with the present invention;

4D is a plan view of an exemplary circuit substrate having an approximately symmetrical form factor, in some embodiments in accordance with the present invention;

4E is a plan view of an exemplary circuit substrate having an approximately symmetrical form factor, in some embodiments according to the invention;

5A is a plan view illustrating an exemplary circuit substrate including a rectifier circuit and an LED string circuit coupled to a capacitor in some embodiments in accordance with the present invention;

5B is a plan view of an exemplary circuit substrate having an approximately asymmetric form factor, in some embodiments in accordance with the present invention;

5C is a plan view of an exemplary circuit substrate having an approximately asymmetric form factor, in accordance with some embodiments of the present invention;

5D is a plan view of an exemplary circuit substrate having an approximately asymmetric form factor, in some embodiments in accordance with the present invention;

Figure 5E is a plan view of an exemplary circuit substrate having an approximately asymmetric form factor, in some embodiments according to the invention;

5F is a plan view of an exemplary circuit substrate having an approximately asymmetric form factor, in some embodiments according to the invention;

6-9 are cross-sectional views illustrating a method of forming a solid state device using a mold on a circuit substrate including mounted chip-on-board LEDs thereon, in accordance with certain embodiments of the present invention;

10-12 are cross-sectional views illustrating methods of forming solid state light emitting devices including chip-on-board LEDs using an encapsulant barrier on a circuit substrate in accordance with certain embodiments of the present invention;

13A is a schematic circuit diagram illustrating an LED driver circuit coupled to an LED string circuit in accordance with some embodiments of the present invention;

13B to 13D are schematic circuit diagrams illustrating current shunt circuits in some embodiments according to the present invention;

Figure 13E is a schematic circuit diagram illustrating an LED driver circuit coupled to an LED string circuit in accordance with some embodiments of the present invention;

Figure 14 is a table showing performance data for exemplary solid state light emitting devices in accordance with certain embodiments of the present invention;

Figure 15 is a table showing performance data for exemplary solid state light emitting devices in accordance with certain embodiments of the present invention;

Figure 16 is an exemplary solid state light emitting device housed in a lighting fixture in accordance with some embodiments of the present invention.

detailed description

Embodiments of the present inventive subject matter will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the inventive subject matter are shown. However, the inventive subject matter may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive subject matter to those skilled in the art. Like reference numerals refer to like elements throughout.

The phrase "light emitting device" as used herein is not limited to merely indicating that the device is capable of emitting light. That is, a light emitting device may be a device that illuminates an area or space such as a building, a swimming pool or a bathing center, a room, a warehouse, an indicator, a road, a parking lot, a vehicle, a sign such as a road sign, a billboard, a ship, a toy, Devices or arrays of devices for mirrors, containers, electronic devices, boats, airplanes, stadiums, computers, remote audio equipment, remote video equipment, cellular phones, trees, windows, LCD displays, caves, tunnels, yards, lampposts, or illuminated fences, Or devices for edge lighting or backlighting (such as backlit posters, signs, LCD displays), light bulb replacement (such as for replacing AC incandescent lamps, low voltage lamps, fluorescent lamps, etc.), lamps for outdoor lighting, lights for security lighting, lights for exterior lighting (wall mounts, pole/post mounts), ceiling fixtures/sconces, under closet lighting, electric lights (floor and/or tables and/or desks), Landscape lighting, track lighting, task lighting, custom lighting, ceiling fan lighting, archive/art display lighting, high vibration/shock lighting, task lights, etc., mirror/vanity lighting, and any other light emitting device.

The subject of the invention further relates to an illuminated enclosure, the space of which can be illuminated uniformly or non-uniformly, comprising an enclosed space and at least one lighting device according to the subject-matter of the invention, wherein the lighting device (homogeneously or non-uniformly ground) illuminates at least a portion of the enclosed space.

Figure 1 is a schematic block diagram illustrating a solid state light emitting device 101 in some embodiments according to the present invention. According to FIG. 1 , a solid state lighting device 101 includes a light emitting diode (LED) driver circuit 105 coupled to an LED string circuit 110 , both mounted on a surface of a substrate 100 . LED driver circuit 105 is coupled to an AC voltage capable of providing current and voltage to LED string circuit 110 and other circuits included in device 101 to emit light from solid state lighting device 101 .

It should be appreciated that the embodiments presented herein are capable of applying AC voltage directly to the device 101 (from an external power source) without including an "on-board" switching mode. In some embodiments in accordance with the invention, LED driver circuit 105 can instead provide a rectified AC voltage to LED string circuit 110, providing acceptable light from the solid state lighting device 101 based on the AC voltage signal provided directly to the device. . It should further be appreciated that a solid state light emitting device 101 according to the present invention can be used in any form of lighting fixture, such as that shown in FIG. 16 .

The LED driver circuit 105 can include components for rectifying the AC voltage, components for providing a current source to the LED string circuit 110, components for a current shunt circuit, components for a current limiting circuit (to limit the current flow through the LED string circuit 110 current flow of at least one LED) and at least one energy storage device, such as a capacitor. It should be further understood that at least some of these components can be mounted on substrate 100 as discrete electronic component packages in some embodiments according to the invention. Still further, in some embodiments according to the invention, some of the remaining circuitry described herein can be integrated into a single integrated circuit package assembled on substrate 100 .

The LED string circuit 110 can include a plurality of “chip on board” (COB) LED groups, coupled in series with each other, mounted on the substrate 100 . Therefore, chip-on-board LEDs can be mounted on the substrate 100 without additional packaging, unless these LEDs are used in other applications that would otherwise include additional packaging, in which, for example, the LEDs are mounted to sub-safety Dismantling sub-mounts, intermediate substrates or other chip carriers that assemble LEDs, etc. Such other approaches are described, for example, in co-pending copending U.S. Patent Application Serial No. 13/192,755 (Attorney Docket No. 5308-1364), where, for example, LEDs may be located on the submount, on the lower base above to provide a stacked structure.

It should also be understood that in some embodiments according to the invention, the LED string circuit 110 can utilize packaged LED devices instead of COB LEDs. For example, in some embodiments according to the invention, LED string circuit 110 can include XML-HV LEDs available from Cree, Inc. of Durham, NC.

Therefore, device 101 can take the form of a relatively small form factor circuit board that couples directly to the AC voltage signal and provides the rectified AC voltage signal to string circuit 110 without using an on-board switched mode power supply. Additionally, the string circuit 110 may consist of COB LEDs or LED devices on a circuit board.

Substrate 100 may be provided in any relatively small form factor (symmetrical or asymmetrical), such as those described herein with reference to Figures 4D, 4E, and 5A-5C. Furthermore, in some embodiments according to the present invention, the resulting small circuit board includes thereon COB LEDs or LED devices operated by direct application of an AC voltage signal (without on-board switched mode power supply), enabling small package , a light-emitting device 101 capable of outputting efficiently, for example, the properties listed in detail in the tables shown in FIG. 14 and FIG. 15 .

It should be understood that the term "mounting" as used herein includes physically connecting components (such as chip-on-board LEDs) to substrate 100 without the use of, for example, co-assigned U.S. Patent Application Serial No. 13/192,755 (Attorney Docket No. 5308) referenced above. -1364), those configurations of intermediate submounts, bases, carriers, or other surfaces. Thus, components described as being "mounted" on a substrate may be on the same surface of the substrate or on opposing surfaces of the same substrate. For example, a component that is placed and soldered on the same substrate during assembly can be described as being "assembled" on that substrate.

It should be understood that the AC voltage signal may have any amplitude sufficient to operate the device 101 in some embodiments according to the invention. For example, in some embodiments according to the invention, the AC voltage signal may be 90 VAC, 110 VAC, 220 VAC, 230 VAC, 277 VAC, or any intermediate voltage. In some embodiments according to the invention, the AC voltage signal is provided from a single-phase AC voltage signal. However, in some embodiments according to the invention, the AC voltage signal can be provided via the voltage signal from two leads of the three-phase AC voltage signal. Therefore, an AC voltage signal can be provided from a higher voltage AC voltage signal regardless of phase. For example, in some embodiments according to the invention, the AC voltage signal can be provided from a three-phase 600 volt AC signal. In still further embodiments according to the present invention, the AC voltage signal may be a relatively low voltage signal, such as 12 volts AC.

FIG. 2 is a schematic block diagram illustrating the solid state light emitting device 101 shown in FIG. 1 in some embodiments according to the present invention. According to FIG. 2, the LED driver circuit 105 includes a rectifier circuit 205 coupled to a current shunt circuit 210 and an LED string circuit 110 comprising a plurality of LED strings coupled in series with each other. As further shown in FIG. 2 , a current splitter circuit 210 is coupled to selected nodes between the LED groups in string 110 .

The current shunt circuit 210 can be configured to operate in response to bias state transitions of the respective groups of LEDs across which the current shunt circuit 210 is connected. Therefore, in some embodiments according to the invention, groups of LEDs within a string can be activated and deactivated incrementally in response to the bias state of the devices in the group. For example, when a rectified AC voltage is applied to LED string circuit 110, certain circuits of the current shunt circuit can be activated and deactivated in response to forward biasing of the LED groups. The current shunt circuit can include a number of transistors configured to provide individually controllable current shunt paths around the number of LED groups between selected nodes to which the current shunt circuit 210 is coupled. These transistors can be turned on/off by the bias transition of the LED group, which can be used to affect the bias of these transistors. Current shunt circuits operating in conjunction with LED strings are further described, for example, in co-pending US Patent Application Serial No. 13/235,127 (Attorney Docket 5308-1461).

As further shown in FIG. 2 , the rectifier circuit 205 , the current shunt circuit 210 and the LED string circuit 110 can be mounted on the substrate 100 such that each of these components is provided on a single surface of the substrate 100 . In other embodiments according to the invention, some of the circuits described herein are mounted on a first side of the substrate 100 while the remaining circuits are mounted on the opposite side of the substrate 100 . However, in some embodiments according to the invention, the circuits described herein are mounted on substrate 100 without the use of intervening substrates, submounts, carriers, or stack-up assemblies that are sometimes used to provide conventional structures. Types of other types of surfaces.

In some embodiments according to the invention, at least some of the components described with reference to FIG. 2 can be mounted on substrate 100 as discrete electronic component packages. Still further, in some embodiments according to the invention, some of the remaining circuitry described with reference to FIG. 2 can be integrated into a single integrated circuit package mounted on substrate 100 .

Still referring to FIG. 2 , an exemplary solid state light emitting device 101 was built and operated according to the parameters shown in the table of FIG. 14 . Specifically, device 101 utilizes a current shunt circuit coupled to string circuit 110 as shown in FIG. 13 instead of the current limiter circuit and capacitor shown in FIG. 13 . The device consists of 12 high voltage 16-junction COB LEDs, each measuring approximately 1.4mm x 1.4mm x .170mm. The data in the table of FIG. 14 shows that the demonstration circuit board provides lumens (Lm) ranging from about 704Lm to about 816Lm at efficiencies (lumens per watt) ranging from about 71Lm/W to about 79Lm/W, providing available Acceptable color point and relatively high power factor. It should be understood, however, that in some embodiments according to the invention, higher outputs can be achieved by, for example, increasing the number of COB LEDs on a circuit board or by increasing the current level used to drive the COB LEDs.

3 is a schematic block diagram illustrating a solid state lighting device 101 comprising an LED driver circuit 105 (comprising a rectifier circuit 205 and a current shunt circuit 210) coupled to a current limiter circuit 305 in parallel with a capacitor 310, Both are in series with the LED string circuit 110 and both can be mounted on the surface of the substrate 100 .

It should be appreciated that current limiter circuit 305 and capacitor 310 can be used to reduce flicker that might otherwise be produced by the AC voltage provided to solid state lighting device 101 . For example, capacitor 310 may be used to store energy near the peak voltage and use the stored energy to drive LED string 110 when the AC voltage magnitude is less than that required for the forward configuration of the LEDs in string 110 . Still further, current limiter circuit 305 can be configured to direct current to capacitor 310 such that energy is stored therein or configured to discharge charge in capacitor 310 through LED string 110 .

Although FIG. 3 shows capacitor 310 for storing and transferring energy, it should be understood that any type of electronic energy storage device can be used in place of or in combination with capacitor 310, such as an inductor. It should be understood that the use of a current limiter circuit in conjunction with an LED string circuit is further described, for example, in co-pending US Patent Application Serial No. 13/235,103 (Attorney Docket No. 5308-1459).

In some embodiments according to the invention, the components shown in FIG. 3 can be mounted on the same surface of the substrate 100 . In other embodiments according to the invention, some of the circuitry shown in FIG. 3 can be mounted on a first surface of substrate 100 while the rest of the circuitry is mounted on a second, opposing surface of substrate 100 . In some embodiments according to the present invention, the LEDs included in the LED string circuit 110 may be chip-on-board LEDs, which may be mounted on either surface of the substrate 100 or in a submount coupled to the substrate 100. abutment or other substrate, as described, for example, in co-pending US Patent Application Serial No. 13/192,755 (Attorney Docket Nos. 5308-1364).

Still referring to FIG. 3 , an exemplary solid state light emitting device 101 was constructed to provide the data presented in the table of FIG. 15 . Specifically, device 101 utilizes a current shunt circuit coupled to string circuit 110 as shown in FIG. 13 , together using a current limiter circuit and capacitor as shown in FIG. 13 . The device consists of 12 high voltage 16-junction COB LEDs, each measuring approximately 1.4mm x 1.4mm x .170mm. The data in the table of Figure 14 shows that the exemplary circuit board provides a range of Lm from about 674Lm to about 785Lm within an efficiency range of from about 69Lm/W to about 74Lm/W, providing an acceptable color point and relatively high power factor. It should be understood, however, that in some embodiments according to the invention, higher outputs can be achieved by, for example, increasing the number of COB LEDs on a circuit board or by increasing the current level used to drive the COB LEDs.

4A is a plan view illustrating a solid state light emitting device 101 comprising a substrate 100 including LED driver circuitry 105 and LED string circuitry 110 mounted on its surface in some embodiments according to the invention. Figure 4B is a cross-sectional view of a portion of the solid state light emitting device 101 shown in Figure 4A in some embodiments according to the invention. 4C is an alternate cross-sectional view of a portion of a solid state light emitting device 101 in which the substrate 100 includes a thermally conductive fillet 417 embedded therein, opposite the LED string circuit 110, in some embodiments according to the invention.

According to FIG. 4A , in some embodiments according to the present invention, the substrate 100 may be a printed circuit board (PCB). PCBs can be formed from many different materials, which can be arranged to provide the desired electrical isolation and high thermal conductivity. In some embodiments, the PCB can at least partially include an insulator to provide the desired electrical isolation. In other embodiments according to the present invention, the PCB can comprise ceramic materials such as alumina, aluminum nitride, silicon carbide or polymeric materials such as polyimide and polyester, among others.

For boards made of materials such as polyimide and polyester, these boards can be flexible (sometimes called flexible printed circuit boards). This can allow the circuit board to take a non-planar or curved shape, so that the LED chips are also arranged in a non-planar form. In some embodiments according to the invention, the circuit board can be a flexible printed substrate such as DuPont's Polyimide. In some embodiments according to the invention, the circuit board may be a standard FR-4 PCB.

This can help to provide circuit boards with different emission patterns, the non-planar shape allowing for less directional emission patterns. In some embodiments according to the invention, this arrangement can allow for more omnidirectional lighting, such as at a lighting angle of 0-180°. In some embodiments according to the invention, the PCB can include highly reflective materials, such as reflective ceramics or metallic layers such as silver, to enhance light harvesting from the components.

In some embodiments, the PCB can include an insulating layer 50 to provide electrical isolation, while also including an electrically neutral material to provide good thermal conductivity. Different insulating materials can be used for the insulating layer, including epoxy-based insulators containing different electrically neutral thermally conductive materials. Many different materials can be used, including but not limited to aluminum oxide, aluminum nitride (AlN) boron nitride, diamond, etc. According to the present invention, different insulating layers can provide different levels of electrical insulation, and some embodiments provide electrical insulation breakdown in the range of 100 to 5000 volts. In certain embodiments, the insulating layer is capable of providing electrical isolation in the range of 1000 to 3000 volts. In other embodiments, the insulating layer is capable of providing electrical isolation with a breakdown of approximately 2000 volts. In some embodiments according to the invention, the insulating layers can provide different levels of thermal conductivity, some having a thermal conductivity in the range of 1-40 w/m/k. In some embodiments, the insulating layer can have a thermal conductivity greater than 10 w/m/k. In other embodiments, the insulating layer can have a thermal conductivity of approximately 3.5 w/m/k.

The insulating layer can have many different thicknesses to provide the desired electrical insulation and thermal conductivity characteristics, such as in the range of 10 to 100 micrometers (μm). In other embodiments, the insulating layer can have a thickness in the range of 20 to 50 (μm). In other embodiments, the insulating layer can have a thickness of approximately 35 (μm).

In some embodiments according to the invention, substrate 100 may be a metal-based PCB, such as a "Thermal-Clad" (T-Clad) insulating substrate material available from Bergquist Corporation of Chanhassen, MN. The "Thermal-Clad" substrate reduces thermal resistance and conducts heat more efficiently than standard circuit boards. The MCPCB can also include a substrate on an insulating layer, opposite the LED string circuit 110, and can include a thermally conductive material to help spread the heat. The substrate can comprise different materials such as copper, aluminum or aluminum nitride. The substrate may have a different thickness, such as in the range of 100 to 2000 μm, while other embodiments may have a thickness in the range of 200 to 1000 μm. Certain embodiments may have a thickness of approximately 500 μm.

Such substrates can be mechanically robust compared to thick film ceramic and direct copper arrangements. Therefore, the metal-based printed circuit board is able to efficiently transfer the heat generated by the LEDs included in the LED string circuit 110 away from the solid state light emitting device 101 . However, it should be understood that the substrate 100 may be any material suitable for mounting the LED driver circuit 105 and the LED string circuit 110 thereon that provides sufficient thermal conduction from the LED string circuit 110 .

In some embodiments, the MCPCB includes a solder mount layer on the bottom surface of the substrate, made of a material suitable for direct mounting to a heat sink, such as by solder reflow. These materials can include one or more layers of different metals such as nickel, silver, gold, palladium. In some embodiments, the buildup layer can include nickel and silver layers, such as nickel with a thickness in the range of 2 to 3 μm and silver in the range of 0.1 to 1.0 μm. In some embodiments, the assembly layer can include other stacks such as approximately 5 μm electroless nickel, approximately 0.25 μm electroless palladium, and approximately 0.15 μm immersion gold. Soldering the MCPCB directly to the heat sink enhances heat dissipation from the board to the heat sink by increasing the thermal contact area between the two. This can improve both vertical and horizontal heat transfer. In certain embodiments according to the present invention, MCPCBs are capable of providing different levels of thermal signature with approximately 0.4°C/W to backside junction performance.

The size of the substrate 100 can vary depending on various factors, such as the size and number of chip-on-board LEDs mounted thereon. For example, in some embodiments, the base may be approximately 33mm on each side. In some embodiments according to the invention, the component-on-substrate may exhibit a height of about 2.5 mm. Other dimensions for substrate 100 may also be used.

It should be appreciated that the substrate 100 can be used in conjunction with heat sinks assembled or incorporated into the respective substrates to provide sufficient thermal conduction from the solid state light emitting device 101, as shown in Figure 4C. In some embodiments in accordance with the invention, a flexible thermally conductive tape, such as GRAFIHX ^™ from GraphTech International, Inc. of Lakewood, Ohio, may be used to couple the heat sink to the substrate 100 . The heat sink can be any efficient thermally conductive material that allows the substrate 100 to conduct heat sufficiently. For example, the heat sink can be metal, such as aluminum. In some embodiments according to the invention, the heat sink is graphite. In some embodiments according to the invention, the heat sink includes a reflective surface to improve light harvesting.

As further shown in FIG. 4A , solid state lighting device 101 includes LED driver circuitry 105 mounted on its surface, along with a plurality of chip-on-board LEDs (sometimes called COB LED array). In some embodiments according to the present invention, the COB LEDs of the string 110 may be arranged in a specific pattern in the approximate center of the substrate 100 . However, it should be understood that the COB LEDs can be arranged in any manner suitable to provide a desired light output from the solid state lighting device 101, for example, the COB LEDs can be arranged in an approximately circular array, a rectangular array, a random array, or a semi-random array. In some embodiments in accordance with the present invention, COB LEDs can be assembled on a single circuitized substrate 100, reducing dead space between COB LEDs, which can reduce the size of the solid state lighting device 101 or the distribution within the device 101. Dimensions of the base 100 are given.

In COB implementations, microchips or dies such as LEDs are assembled and electrically interconnected to their final circuit substrates, rather than being traditionally assembled or packaged as individual LED packages or integrated circuits. Conventional device packaging is eliminated when COB assembly is used, the overall process of design and manufacturing can be simplified, space requirements can be reduced, cost can be reduced and performance can be improved as a result of shorter interconnection paths. The COB process can include three main steps: 1) LED die attach or die assembly; 2) wire bonding; and 3) packaging the die and leads. These COB layouts can also provide further advantages, allowing direct assembly and interfacing with the host device heat sink.

In certain embodiment LED array embodiments, each chip in the array can have its own lens formed thereon to facilitate light acquisition and emission on the first pass. First-pass light acquisition/emission refers to the light emitted from a specific LED chip passing through the respective lens, and the first pass of light from the LED chip to the surface of the main lens. That is, light is not reflected back, such as by total internal reflection (TIR), where some light may be absorbed. This primary emission can enhance the luminous efficiency of the LED assembly by reducing the LED light that may be absorbed. Certain embodiments can include a high density of light emitting components while maximizing light harvesting, which can increase the efficiency of the respective solid state light emitting devices. Certain embodiments according to the invention can be arranged in subgroups of LED chips within an array, each subgroup having its own main lens for improved light extraction. In some embodiments, the lens may be hemispherical, which can further increase light harvesting by providing a lens face that facilitates first pass light emission.

In some embodiments according to the invention, the LED array can include LED chips emitting light of the same color or different colors (such as red, green and blue LED chips or subgroups, white LED and red LED chips or subgroups, etc.) . Techniques have been developed to generate white light from multiple discrete light sources to provide a desired CRI at a desired color temperature, utilizing different hues from different discrete light sources. Such techniques are described in US Patent No. 7,213,940, entitled "Lighting Device and Lighting Method," the contents of which are incorporated herein by reference.

In some embodiments, secondary lenses or optics may be used in addition to primary lenses or optics, such as larger secondary optics covering groups of light emitting devices with primary optics. Using each light emitting device or group of light emitting devices with its own main lens or optics can exhibit greater scalability to more easily provide larger arrays of LEDs according to embodiments of the present invention. In some embodiments according to the invention, LED string circuit 110 can include several hundred COB LEDs.

In some embodiments, the LED array may be a COB mounted to the substrate 100, with features that provide improved operation. Substrate 100 can provide electrical isolation features, allowing board-level electrical isolation of COB LEDs. At the same time the circuit board can have several properties that provide an efficient thermal path to dissipate heat from the COB LED. Efficient heat dissipation of COB LEDs can lead to improvements in reliability and color consistency of LED chips. The base 100 can also be arranged to allow efficient assembly of the main heat sink. In some embodiments according to the invention, the base 100 includes features that allow it to be easily and efficiently assembled to a heat sink using mechanical tools. In other embodiments, the circuit board can include materials that allow it to be efficiently and reliably soldered to the heat sink, such as through a reflow process.

The present invention can provide scalable LED array layouts, enabling certain embodiments to have as few as three light emitting devices, while others may have as many as tens or hundreds of light emitting devices.

It should be further understood that certain components in the LED driver circuit 105 may be discrete electronic component packages mounted on the substrate 100 to provide, for example, multiple current shunt circuits mounted on the surface of the substrate 100 . It should be further understood that other electronic component packages may be provided on the substrate 100 to provide the remaining circuitry included in the solid state light emitting device 101 .

According to FIG. 4B , the substrate 100 may be a metal-based multilayer PCB including an upper metal layer for providing interaction between electronic component packages on the surface of the substrate 100 . The lower metal (or base) layer 415 can be used to facilitate heat transfer from the LED string circuit 110 and can be relatively thick compared to the upper metal layer 405 . The upper metal layer 405 and the lower metal layer 415 are separated by a thermally conductive insulating layer 410 capable of electrically insulating the upper metal layer 405 from the lower metal layer 415 while still providing a thermal path from the LED string circuit 110 to the lower metal layer 415 .

Therefore, the lower metal layer 415 can provide a heat sink for heat dissipation from the LED string circuit 110 . In yet further embodiments in accordance with the present invention, a secondary heat sink can be attached to the lower surface of the lower metal layer 415 to provide supplemental heat transfer from the LED string circuit 110 .

In some embodiments according to the invention, the lower metal layer 415 may be a metal such as aluminum, copper, or beryllium oxide. In some embodiments according to the invention, thermally conductive insulating layer 410 may be a filler matrix composition that acts as a soldering medium as well as a thermal pathway for heat conduction, as well as providing an insulating layer between upper metal layer 405 and lower metal layer 415 . In some embodiments according to the invention, the thermal conductivity of the thermally conductive insulating layer 410 may be about 4 times to about 16 times greater than conventional FR4 insulators.

Although Figure 4B shows a single (ie upper) metal layer 405, other embodiments according to the invention can also be provided where additional signal layers are provided as part of the metal-based PCB. For example, in some embodiments according to the invention, an additional metal layer 405 may be provided within a thicker thermally conductive insulating layer 410 to provide two or more layers in some embodiments according to the invention Multi-base printed circuit boards. In still further embodiments according to the present invention, an additional thermally conductive insulating layer may be provided below the lower metal layer 415 such that the lower metal layer 415 is within the metal-based printed circuit board rather than on its exposed surface.

According to FIG. 4C , a flexible printed circuit board is provided as the substrate 100 on which the LED string circuit 110 is mounted. A thermally conductive fillet 417 can be embedded within the substrate 100 proximate to the LED string circuit 110 to provide heat dissipation from the LED string circuit 110 . In some embodiments according to the invention, the thermally conductive fillet 417 may be a metal such as copper, aluminum, or beryllium oxide. Other thermally conductive materials may also be used.

4D is a plan view of an exemplary circuit substrate having an approximately symmetrical form factor, in some embodiments according to the invention. According to FIG. 4D , six LEDs (as part of the string circuit 110 ) are mounted on the central portion 460 of the substrate 100 on which the AC voltage source input J1 is mounted near the outer edge. As shown in FIG. 4D , according to the desired light output from the device 101 , the LEDs adopt a first layout in the central portion 460 . In some embodiments according to the present invention, the plurality of LEDs are separated from the rest of the electronic components mounted on the substrate 100 by the remaining portion 465 of the substrate 100, wherein other electronic components are only mounted on the remaining portion of the substrate 100 on the substrate 100 between 465 and the outer perimeter 470 . In some embodiments according to the invention, other electronic components are mounted in the retaining portion 465 .

Still referring to FIG. 4D , an exemplary embodiment according to the present invention is constructed in which the center of the LED in the central portion 460 is located at the center of the substrate 100 . The shown setup uses six XTE-HV LEDs from Cree, Durham, NC, producing about 2000 lumens at about 85 degrees Celsius. The diameter of the central portion 460 is approximately 21mm and the dimensions of the entire plate are approximately 54mm x 60mm. The dimension of the reserved portion 465 is again 9.5 mm beyond the central portion 460 . The total power provided to the device was about 31.4W, of which about 20.6W was dissipated by the LEDs, for a total power consumption of device 101 of 25.2W.

4E is a plan view of an exemplary circuit substrate having another approximately symmetrical form factor, in some embodiments according to the invention. According to FIG. 4E , five LEDs (as part of the string circuit 110 ) are mounted on the central portion 460 of the substrate 100 on which the AC voltage source input J1 is mounted near the outer edge. As shown in FIG. 4E , depending on the desired light output from device 101 , the LEDs adopt a second layout in central portion 460 . In some embodiments according to the present invention, the plurality of LEDs are separated from the rest of the electronic components mounted on the substrate 100 by the remaining portion 465 of the substrate 100, wherein other electronic components are only mounted on the remaining portion of the substrate 100 on the substrate 100 between 465 and the outer perimeter 470 . In some embodiments according to the invention, other electronic components are mounted in the retaining portion 465 .

Still referring to FIG. 4E , an exemplary embodiment according to the present invention is constructed in which the center of the LED in the central portion 460 is located at the center of the substrate 100 . The setup shown uses five XTE-HV LEDs from Cree, Durham, NC, producing approximately 800 lumens at approximately 85 degrees Celsius. The diameter of the central portion 460 is approximately 16.1mm and the dimensions of the entire plate are approximately 54mm x 54mm. The dimension of the reserved portion 465 is again 9.5 mm beyond the central portion 460 . The total power provided to the device was about 13.9W, of which about 9.5W was consumed by the COB LEDs, the total power consumption of the device 101 was 11.5W.

5A is a plan view illustrating a solid state light emitting device 101 including LED string circuitry 110 and LED driver circuitry 105 mounted on a substrate 100 and including capacitors in some embodiments according to the invention. It should be understood that the LED driver circuit 105 shown in FIG. 5 can also include multiple shunt circuits as described herein, as well as a current limiter circuit 305 working in conjunction with a capacitor 310 to provide operation of the LED string circuit 110 described herein. It should be further understood that capacitor 310 can be mounted on a substrate to reduce the possibility that the outline of capacitor 310 could introduce shadows into the light emitted by solid state light emitting device 101 . Therefore, the capacitor 310 may be located near the outer periphery of the substrate 100 .

The size of the substrate 100 can vary depending on various factors, such as the size and number of chips-on-board mounted thereon. For example, in some embodiments, the base may be approximately 33mm x 46mm rectangular. In some embodiments according to the invention, the components on the substrate may exhibit a height approximately equal to the height of the capacitor 310 . In some embodiments according to the invention, the components on the substrate may exhibit a height approximately equal to 13.5 mm. Other dimensions for substrate 100 may also be used.

5B is a plan view of an exemplary circuit substrate having an approximately asymmetric form factor, in some embodiments according to the invention. According to FIG. 5B , six LEDs (as part of the string circuit 110 ) are mounted on the side portion 560 of the substrate 100 . As shown in FIG. 5B , depending on the desired light output from the device 101 , the LEDs are arranged in a first layout in the side portion 560 and the AC voltage source input J1 is fitted on the substrate 100 near the outer edge. In some embodiments according to the present invention, the plurality of LEDs are separated from the remaining electronic components assembled to the substrate 100 by the remaining portion 565 of the substrate 100, wherein other electronic components are only mounted on the remaining portion of the substrate 100 on the substrate 100 565 and the outer perimeter 570 . In some embodiments according to the invention, other electronic components are mounted in the retaining portion 565 .

Still referring to FIG. 5B , an exemplary embodiment according to the present invention is constructed wherein the center of the LEDs in the central portion 560 is located approximately 17.5 mm from the top and bottom edges of the substrate 100 and approximately 15.2 mm from the right edge. The setup shown uses six XTE-HV LEDs from Cree, Durham, NC, producing approximately 2000 lumens at approximately 85 degrees Celsius. The diameter of the central portion 560 is approximately 21mm and the dimensions of the entire plate are approximately 71.3mm x 35mm. The dimension of the reserved portion 565 is again 9.5 mm outside the central portion 560 . The total power provided to the device was about 31.4W, of which about 20.6W was dissipated by the LEDs, for a total power consumption of device 101 of 25.2W.

5C is a plan view of an exemplary circuit substrate having an approximately asymmetric form factor, in some embodiments according to the invention. According to FIG. 5C , five LEDs (as part of the string circuit 110 ) are mounted on the side portion 560 of the substrate 100 . As shown in FIG. 5C , depending on the desired light output from the device 101 , the LEDs are arranged in a second layout in the side portion 560 and the AC voltage source input J1 is fitted on the substrate 100 near the outer edge. In some embodiments according to the present invention, the LED is separated from the remaining electronic components mounted on the substrate 100 by the remaining portion 565 of the substrate 100, wherein other electronic components are only mounted on the remaining portion 565 of the substrate 100 on the substrate 100 and between 570 on the outer periphery. In some embodiments according to the invention, other electronic components are mounted in the retaining portion 565 .

Still referring to FIG. 5C , an exemplary embodiment in accordance with the present invention was constructed wherein the center of the LEDs in central portion 560 was located approximately 16.2 mm from the top and bottom edges of substrate 100 and approximately 12.827 mm from the right edge. The setup shown uses five XTE-HV LEDs from Cree, Durham, NC, producing approximately 800 lumens at approximately 85 degrees Celsius. The diameter of the central portion 560 is approximately 16.1mm and the overall plate measures approximately 66.875mm x 32.4mm. The dimension of the reserved portion 565 is again 9.5 mm outside the central portion 560 . The total power provided to the device was about 13.9W, of which about 9.5W was dissipated by the LEDs, for a total power consumption of device 101 of 11.5W.

5D is a plan view of an exemplary circuit substrate having an approximately asymmetric form factor, in some embodiments according to the invention. According to FIG. 5D , a single LED (as part of the string circuit 110 ) is mounted on the side portion 560 of the substrate 100 . Depending on the desired light output from the device 101 , a single LED is arranged in the side portion 560 and an AC voltage source input J1 is fitted on the substrate 100 near the outer edge. In some embodiments according to the present invention, the LED is separated from the remaining electronic components mounted on the substrate 100 by the remaining portion 565 of the substrate 100, wherein other electronic components are only mounted on the remaining portion 565 of the substrate 100 on the substrate 100 and between 570 on the outer periphery. In some embodiments according to the invention, other electronic components are mounted in the retaining portion 565 .

Considering the above description with reference to FIGS. light output. For example, using 4 XTE-HVLEDs (and the current to drive the LEDs) can provide other embodiments to produce 600 lumens. In some embodiments according to the invention, 1000 lumens can be produced using 3 XTE-HV LEDs. Other combinations of lumens and numbers and types of COB LEDs can also be used to provide embodiments in accordance with the present invention.

Therefore, embodiments in accordance with the present invention can provide relatively small substrates that do not include on-board switching mode power supplies, but emit light of relatively high brightness. For example, in some embodiments according to the invention, the substrate can occupy an area of about 3240 ^mm2 or less while emitting at least 2000 lumens. Furthermore, in some embodiments according to the present invention, the portion of the substrate utilized by the LED (or COB LED) can be approximately 1384 mm ² or less. In some embodiments according to the present invention, LEDs (or COB LEDs) can utilize about 40% or less of the total area of the substrate. In some embodiments according to the invention, the remaining portion adjacent to the portion of the substrate utilized by the LED (or COB LED) may be about 16% or more of the length (ie length or width) of the largest dimension of the substrate.

In a further embodiment according to the present invention, the substrate is capable of occupying an area of about 2900 mm ² or less while emitting at least 800 lumens. Furthermore, in some embodiments according to the present invention, the portion of the substrate utilized by the LED (or COB LED) can be approximately 814 mm ² or less. In some embodiments according to the invention, the LED (or COB LED) can utilize about 30% or less of the total area of the substrate. In certain embodiments according to the invention, the remaining portion adjacent to the portion of the substrate utilized by the LED (or COB LED) may be about 18% or more of the length (ie length or width) of the largest dimension of the substrate.

In a further embodiment according to the present invention, the substrate is capable of occupying an area of approximately 3240 mm ² or less while emitting at least 2000 lumens. Furthermore, in some embodiments according to the present invention, the portion of the substrate utilized by the LED (or COB LED) can be approximately 1384 mm ² or less. In some embodiments according to the present invention, LEDs (or COB LEDs) can utilize about 40% or less of the total area of the substrate. In certain embodiments according to the invention, the remaining portion adjacent to the portion of the substrate utilized by the LED (or COB LED) may be about 13% or more of the length (ie length or width) of the largest dimension of the substrate.

In a further embodiment according to the present invention, the substrate is capable of occupying an area of about 2144 mm ² or less while emitting at least 800 lumens. Furthermore, in some embodiments according to the present invention, the portion of the substrate utilized by the LED (or COB LED) can be approximately 814 mm ² or less. In some embodiments according to the invention, the LED (or COB LED) can utilize about 38% or less of the total area of the substrate. In certain embodiments according to the invention, the remaining portion adjacent to the portion of the substrate utilized by the LED (or COB LED) may be about 14% or more of the length (ie length or width) of the largest dimension of the substrate.

Figure 5E is a plan view of an exemplary circuit substrate having an approximately asymmetric form factor, in some embodiments according to the invention. According to FIG. 5E , six LEDs (as part of the string circuit 110 ) are mounted on the side portion 580 of the substrate 100 . The LED device may be an LED manufactured by Cree, Inc. of Durham, NC, as described, for example, in Ser. Nos. 13/027,006, filed Feb. 14, 2011; US Patent Application No. 13/112,502 filed on , the disclosure of which is incorporated herein by reference. As shown in FIG. 5E , a first layout is employed in the side portion 580 , each of the LED devices including a respective submount 581 and a respective lens 582 , according to the desired light output from the device. The LED device is electrically coupled to the remaining electronic components on the substrate 100 by conductive leads 583 . In some embodiments according to the present invention, the plurality of LED devices are separated from the remaining electronic components by the remaining portion of the substrate 100 , where the other electronic components are mounted on the substrate 100 outside the remaining portion of the substrate 100 . In some embodiments according to the invention, other electronic components are fitted in the reserved portion.

Figure 5F is a plan view of an exemplary circuit substrate having an approximately asymmetric form factor, in some embodiments according to the invention. According to FIG. 5F , five LEDs (as part of the string circuit 110 ) are mounted on the side portion 590 of the substrate 100 . The LED device may be an LED manufactured by Cree, Inc. of Durham, NC, as described, for example, in Ser. Nos. 13/027,006, filed Feb. 14, 2011; US Patent Application No. 13/112,502 filed on . As shown in Figure 5F, in side portion 590, each of the LED devices includes a respective submount 591 and a respective lens 592, depending on the desired light output from the device. The LED device is electrically coupled to the remaining electronic components on the substrate 100 by conductive leads 593 . In some embodiments according to the present invention, the LED device is separated from the remaining electronic components mounted on the substrate 100 by the remaining portion of the substrate 100 , where other electronic components are mounted on the substrate 100 outside the remaining portion of the substrate 100 . In some embodiments according to the invention, other electronic components are fitted in the reserved portion. It should be further understood that features specifically shown in FIGS. 5E and 5F , such as submounts for the respective LEDs, conductive leads, and remaining electronic components can also be included in the embodiment of FIGS. 4-5D .

6-8 are cross-sectional views illustrating methods of forming solid state light emitting devices in accordance with some embodiments of the present invention. According to FIG. 6 , the chip-on-board LEDs included in the LED string circuit 110 are mounted on the substrate 100 . An encapsulation material 605 is applied over the chip-on-board LED. In some embodiments according to the invention, the encapsulation material 605 provides a continuous layer covering the LED and the portions on the substrate 100 between several adjacent LEDs. Therefore, encapsulation material 605 can be applied to the chip-on-board LEDs substantially simultaneously with each other.

It should be understood that encapsulation material 605 may be used to form lenses on chip-on-board LEDs. In some embodiments according to the present invention, the encapsulation material 605 can include liquid silicone resin and/or liquid epoxy resin, and/or volatile solvent materials such as alcohol, water, acetone, methanol, ethanol, ketone, iso Propyl, hydrocarbon solvents, hexane, ethylene, ethylene glycol, methyl ethyl ketone, and combinations thereof.

In a further embodiment according to the present invention, the portion of the encapsulation material 605 extending between several adjacent chip-on-board LEDs may remain on the substrate 100 after the assembly process is completed, and in some embodiments according to the present invention , the intervening encapsulation material 605 is removed from the substrate 100 . In other embodiments according to the present invention, the encapsulation material 605 can include other materials, such as light conversion materials, diffusion materials, and the like.

According to FIG. 7, the mold 710 is brought into contact with the encapsulation material 605 on the chip-on-board LED. The mold 710 includes a recess 711 in its lower surface, the position of which is opposite to where the chip-on-board LED 4 is to be placed on the substrate 100 . The recess 711 has the shape to give a lens on the chip-on-board LED.

Mold 710 may be any material suitable for molding selected encapsulation material 605 , such as silicone, as a conformal or other contoured layer. In some embodiments according to the invention, mold 710 may be a metal, such as aluminum. In some embodiments according to the invention, mold 710 may be silicon or silicon carbide. Other materials can also be used for the mold 710 .

The mold 710 may have a release material applied thereto. In particular, a release material can be sprayed or otherwise applied to the surface of the mold 710 from which the substrate and chip-on-board LEDs are separated. The release material may be any material that will facilitate removal of the chip-on-board LED and substrate from the mold 710 . In certain embodiments according to the invention, the release material may be a silicone-based release formulation.

It should be understood that even though the encapsulation material 605 extending between several adjacent chip-on-board LEDs on the substrate 100 can be pressed to a relatively thin layer, the encapsulation material 605 can remain on the substrate 100, although not provided as a specific board The lens part of the chip-on-chip LED.

According to FIG. 8 , each chip-on-board LED on the substrate 100 is equipped with a lens 815 formed from the post-molding encapsulation material 605 . In some embodiments according to the present invention, the encapsulation material 605 between several adjacent chip-on-board LEDs shown in FIG. 8 may be removed. It should be further understood that additional layers of encapsulation material 605 may be provided over lens 815 to provide additional optical features to LED string circuit 110 . After the lens 815 is molded, additional discrete electronic component packages may be mounted on the substrate 100 . For example, in some embodiments according to the invention, the discrete electronic component packages making up the LED driver circuit 105 can be assembled to the substrate 100 after the lens 815 is formed from the encapsulation material 605 .

Figure 9 is a cross-sectional view illustrating a method of forming the solid state light emitting device 101 using a mold to form the lens 815 in accordance with some embodiments of the present invention. Specifically, mold 910 further includes discrete electronic component package recesses 911 configured to accommodate the contours of discrete electronic component packages 905 mounted on substrate 100 over the LED strings having encapsulation material 605 thereon. circuit 110 external. Therefore, the discrete electronic component package 905 can be mounted on the substrate 100 together with the chip-on-board LEDs in the string circuit 110 . The encapsulation material 605 can then be applied to the chip-on-board LED, whereupon the mold 910 can be brought into contact with the encapsulation material 605 to form the lens 815, while damage to the discrete electronic package 905 can be avoided by including the discrete electronic package recess 911.

10-12 are cross-sectional views illustrating a method of forming solid state light emitting device 101 in some embodiments according to the invention. According to FIG. 10A , a chip-on-board LED is mounted on a substrate 100 and at least partially surrounded by an encapsulant barrier 1005 on the substrate 100 . It should be understood that the upper surface of the encapsulant barrier 1005 is lower than the upper surface of the chip-on-board LED surrounded by the encapsulant barrier 1005 .

An encapsulant material 1015 is dispensed over the chip-on-board LEDs. In some embodiments in accordance with the invention, nozzle 1110 is used to dispense encapsulant material 1015 over the chip-on-board LED. Encapsulant material 1015 is dispensed in an amount sufficient to provide each respective lens 815 formed on the respective chip-on-board LED. In some embodiments according to the invention, the nozzle 1110 is moved over the chip-on-board LEDs to sequentially dispense encapsulant material 1115 onto each respective chip-on-board LED. For example, the nozzle 1110 may be positioned above the leftmost chip-on-board LED in the first position so that the encapsulant material 1115 is dispensed onto the respective chip-on-board LED just below the nozzle 1110 .

After the encapsulant material 1115 has been dispensed, the nozzle 1110 is moved to a second position immediately above the chip-on-board LED to the immediate right of the leftmost chip-on-board LED. This process can be repeated to dispense encapsulant material 1115 to each chip-on-board LED included in string circuit 110 . In other embodiments according to the invention, a plurality of nozzles 1110 are pre-positioned at at least two chip-on-board LEDs, with encapsulant material 1115 being dispensed onto each chip-on-board LED substantially simultaneously with each other.

The encapsulant barrier 1005 is configured to restrict the flow of encapsulant material 1115 onto the respective chip-on-board LEDs so as to allow the formed lens 815 to have the desired shape 1105 . It should be appreciated that, as shown in FIG. 10B , for example, an encapsulant barrier 1005 can at least partially surround each respective chip-on-board LED. For example, in some embodiments according to the invention, the encapsulant barrier 1005 may completely surround the respective chip-on-board LEDs. In other embodiments according to the invention, the encapsulant barrier 1005 may only partially surround the chip-on-board LED.

In some embodiments according to the invention, the encapsulant barrier 1005 may have periodic or aperiodic gaps formed therein, but still allow the formation of the lens 815 with the desired shape 1105 for the chip-on-board LED. It should also be understood that although sealant barrier 1005 is shown as having a substantially rectangular cross-section, other forms of sealant barrier 1005 may be used. For example, encapsulant barrier 1005 may have a semi-circular shape or other geometric shape that provides sufficient surface tension so that encapsulant material 1115 contributes to shape 1105 when dispensed onto the chip-on-board LED.

In some embodiments according to the invention, the sealant barrier 1005 can have any shape that restricts the flow of the sealant material 1015 . For example, in some embodiments according to the invention, the encapsulant barrier 1005 has a square or rectangular perimeter shape to at least partially surround the chip-on-board LED. Other shapes can also be used.

12 is a cross-sectional view showing removal of encapsulant barrier 1005 from around chip-on-board LED 104 after forming lens 815 with desired profile 1105 . Specifically, the encapsulant barrier 1005 can be etched from the outer edge of the lens 815 at the base of the chip-on-board LED, forming a recess 1205 at the outermost edge of the lens 815 at the surface of the substrate 100 . In some embodiments in accordance with the invention, sealant barrier 1005 is not removed from lens 815 .

13A is a schematic circuit diagram illustrating an LED driver circuit coupled to an LED string circuit, in some embodiments according to the present invention. The device 101 includes a string 110 of LED groups 110-1, 110-2, ..., 110-N connected in series. Each of the LED groups 110-1, 110-2, ..., 110-N includes at least one LED. For example, each of the groups can include a single LED and/or each group can include multiple LEDs in various parallel and/or series arrangements. These groups of LEDs can be arranged in many different ways and can have multiple compensation circuits associated therewith, as described, for example, in co-pending U.S. Patent Application Serial No. 13/235,103 (Attorney Docket: 5308-1459); Discussion in Patent Application Serial No. 13/235,127 (Attorney Docket: 5308-1461).

Power is provided to LED string 110 from rectifier circuit 105 configured to couple to AC power source 10 and generate rectified voltage v _R and current i _R therefrom. The rectifier circuit 105 may be included in the light emitting device 101 or may be part of a separate unit coupled to the device 101 .

The device 101 further comprises respective current splitting circuits 130 - 1 , 130 - 2 , . . . , 130 -N connected to respective nodes of the string 110 . The current shunt circuits 130-1, 130-2, . . . , 130-N are configured to provide current paths that bypass respective ones of the LED groups 110-1, 110-2, . . . , 110-N. Each of the current shunt circuits 130-1, 130-2, . ..., 110-N. Transistor Q1 is biased using transistor Q2, resistors R1, R2, . . . , RN and diode D. Transistor Q2 is configured to function as a diode with its base and collector terminals connected to each other. Different numbers of diodes D are connected in series with transistor Q2 in respective circuits of current shunt circuits 130-1, 130-2, . . . , 130-N such that The base terminals of the current pass transistor Q1 in are biased at different voltage levels. Resistors R1, R2, . . . RN are used to limit the base current of the current pass transistor Q1. The current pass transistor Q1 of the respective current shunt circuit 130-1, 130-2, . . . , 130-N will be turned off at different emitter bias voltages, which is determined by the current flowing through the resistor R0. Therefore, the current shunt circuits 130-1, _130-2 , . . . 110-N are incrementally activated and deactivated as the rectified voltage _vR rises and falls. The current pass transistor Q1 is turned on and off according to the bias state of the LED groups 110-1, 110-2, . . . , 110-N.

As further shown in FIG. 13A, the string 110 of series-connected LED groups is also coupled in series with a current limiter circuit implemented as a current mirror circuit 1420, although any type of current limiter circuit may be used in embodiments according to the invention. One or more storage capacitors 310 are connected in parallel with the string 110 of series-connected LED groups and the current mirror circuit 1420 . The current mirror circuit 1420 may be configured to limit the current through the string 110 of series-connected LED groups to an amount that is less than the rated current supplied to the string circuit 110 .

As further shown in FIG. 13A , the current mirror circuit 1420 includes a first transistor Q1 and a second transistor Q2 connected in a current mirror configuration and resistors R1 , R2 , R3 . The current mirror circuit 1420 can provide a current limit of approximately (V _LED −0.7)/(R1+R2)×(R2/R3). A voltage limiter circuit 1460 , such as a Zener diode, may also be provided to limit the voltage developed across one or more storage capacitors 310 . In this way, one or more storage capacitors 310 may alternately be charged via the rectifier circuit 105 and discharged via the string 110 of series-connected LED groups, which may provide more uniform lighting. Current mirror circuit 1420 is coupled to LED group 1410 , which is included among a plurality of LED groups of string circuit 110 . It should be understood that LED group 1410 can include multiple LEDs connected in parallel with each other.

13B-13D are schematic circuit diagrams illustrating current shunt circuits in some embodiments according to the present invention. Specifically, transistor Q2 shown in FIG. 13A as part of current shunt circuits 130-1 through 130-N is replaced by diode D in FIGS. 13B through 13D to provide sufficient biasing of the respective bases of associated transistors Q1. Additionally, each stage of current shunt circuits 130-1 through 130-N includes a corresponding number of diodes D to provide bias otherwise provided by transistor Q2. For example, the first stage 130-1 includes two diodes for biasing, while the next stage 130-2 includes three diodes for biasing. Not only that, each stage of 130-1 to 130-N can share the diode D of the preceding stage for biasing.

Figure 13E is a schematic circuit diagram illustrating an LED driver circuit coupled to an LED string circuit, in some embodiments in accordance with the present invention. FIG. 13E shows the current shunt circuit of FIG. 13B to FIG. 13D used in place of the current shunt circuits 130-1 to 130-N. According to FIG. 13E, in the first section, the base voltage of Q1 is approximately equal to the voltage drop of (D1+D2). In the second segment, the base voltage of Q2 is approximately equal to the voltage drop of (D1+D2+D3). In the Nth segment, the base voltage of QN is approximately equal to the voltage drop of (D1+D2+...+DN). Therefore, in some embodiments according to the present invention, current shunt circuits can be fabricated as diode arrays and triode blocks. In some embodiments according to the present invention, the diode array and the transistor block can be integrated together or separated from each other.

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

It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present.

It will be understood that when an element or layer is referred to as being "on" another element or layer, the element or layer can be directly on the other element or layer or intervening elements or layers may also be present. In contrast, when an element is referred to as being "directly on" another element or layer, there are no intervening elements or layers present. As used herein, the term "and/or" includes any combination of one or more of the associated listed items.

Spatially relative terms, such as "below", "beneath", "under", "above", "on", etc., may be used herein for ease of description in order to compare one element or feature with another. The relationship of the components is described as shown in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use and operation in addition to the orientation depicted in the figures. Throughout this specification, like reference numerals refer to like elements in the drawings.

Embodiments of the inventive subject matter are described herein with reference to plan and perspective illustrations that are schematic illustrations of idealized embodiments of the inventive subject matter. As such, variations from the shapes shown are to be expected as a result, for example, of manufacturing techniques and/or tolerances. Thus, inventive subject matter should not be construed as limited to the particular shapes of objects illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. Thus, the objects shown in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of the inventive subject matter.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the inventive subject matter. As used herein, the singular forms "an" and "the" are intended to include the plural forms as well unless the context clearly dictates otherwise. It should be further understood that when the terms "comprises" and/or "comprises" are used herein, it specifies the presence of stated features, integers, steps, operations, elements and/or components, but does not exclude one or more other features, integers, The presence or addition of steps, operations, elements, components and/or combinations thereof.

Unless defined otherwise, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the subject matter of the invention belongs. It should be further understood that the terms used herein should be interpreted to have a meaning consistent with their meaning in the relevant art and in the context of this specification, and should not be interpreted in an idealized or overly formal sense, unless explicitly stated herein so defined. The term "plurality" is used herein to refer to two or more referenced items.

It should be understood that, as used herein, the term light emitting diode can include light emitting diodes, laser diodes and/or include one or more semiconductor layers (which can include silicon, silicon carbide, gallium nitride, and/or other semiconductor materials), substrates (which can include graphene, silicon, silicon carbide, and/or other microelectronic substrates) and one or more contact layers (which can include metal and/or other conductive layers).

In the drawings and specification, there have been disclosed typical preferred embodiments of the inventive subject matter and although specific terms have been employed, they have been used in a generic and descriptive sense only and not for purposes of limitation, the scope of the inventive subject matter is as follows stated in the claims.

Claims (42)

1. A solid-state light emitting device, comprising: a rectifier circuit mounted on a surface of a substrate housed in the solid state light emitting device, coupled to an AC voltage source configured to provide a rectified AC voltage to the substrate; strings of light emitting diode LED groups mounted on the surface of said substrate, connected in series with each other and coupled to said rectifier circuit without coupling a switched-mode power supply between said rectifier circuit and said string of LED groups, wherein the string of LED groups is arranged in an LED portion of the substrate comprising an area of LEDs occupying 40% or less of the area of the substrate, the string of LED groups configured to emit light comprising 800 lumens or more light; and a plurality of current shunt circuits mounted on the surface of the substrate, respective current shunt circuits coupled to respective nodes of the strings and configured to respond to a bias state transition of a respective one of the groups of LEDs And operate. 2. The apparatus of claim 1, wherein at least said plurality of current shunt circuits comprise discrete electronic component packages mounted on said substrate. 3. The apparatus of claim 1, wherein the LEDs in the string comprise chip-on-board LEDs mounted on a surface of the substrate. 4. The device of claim 1 , wherein the substrate comprises a flexible circuit substrate, the device further comprising: A heat sink, mounted on an opposing surface of the substrate, is thermally coupled to the string of LED groups. 5. The apparatus of claim 1, wherein the substrate comprises a metal base printed circuit board, MCPCB. 6. The apparatus of claim 5, wherein the MCPCB comprises a metal layer separated from the surface of the substrate by an insulating layer and configured to conduct heat away from the string of LED groups. 7. The apparatus of claim 5, wherein the MCPCB includes an insulating material between the first metal layer and the second metal layer. 8. The apparatus of claim 7, wherein the first metal layer comprises a circuit layer and the second metal layer is configured to conduct heat away from the string of LED groups. 9. The apparatus of claim 1, further comprising: a current limiter circuit, on the surface of the substrate, in series with the rectifier circuit and at least one of the LED groups; and At least one capacitor is coupled across the at least one LED group and the current limiter circuit on the surface of the substrate. 10. The apparatus of claim 9, wherein the current limiter circuit is configured to selectively supply current from the rectifier circuit to the at least one LED group and to the at least one capacitor. 11. The apparatus of claim 1, further comprising: An encapsulant layer, on the surface of the substrate, seals the string of LED groups. 12. The device of claim 11, wherein the sealant layer comprises silicone. 13. The apparatus of claim 1, further comprising: A separate layer of encapsulant separately seals the LEDs in the string of LED groups. 14. The apparatus of claim 1, wherein the rectifier circuit and the plurality of current shunt circuits are included in a single integrated circuit device package. 15. The apparatus of claim 9, wherein the rectifier circuit, the plurality of current shunt circuits, and the current limiter circuit are all integrated in an application specific integrated circuit. 16. The device of claim 1, wherein the substrate comprises a silicon substrate, a gallium nitride substrate, a silicon carbide substrate, or a graphene substrate. 17. The apparatus of claim 1, further comprising: an encapsulant barrier on the substrate, at least partially surrounding the LEDs in the group, configured to reduce flow of the encapsulant material away from the LEDs during application of the encapsulant material to facilitate Lenses are formed on strings. 18. The device of claim 17, wherein the height of the encapsulant barrier above the substrate is less than the height of the upper surface of the LED. 19. The apparatus of claim 1, wherein the string of LED groups comprises at least three groups coupled in series to each other, each of the three groups comprising at least two high voltage LEDs coupled in parallel to each other. 20. The apparatus of claim 1, wherein said AC voltage source comprises at least 110 VAC. 21. The apparatus of claim 1, wherein the string of LED groups comprises at least three groups coupled in series to each other, each of the three groups comprising at least two high voltage LEDs coupled in series to each other. 22. The apparatus of claim 1, wherein said AC voltage source comprises at least 220 VAC. 23. The apparatus of claim 1, wherein at least one of said strings of LED groups comprises at least two high voltage LEDs coupled to each other in parallel or in series, and said AC voltage source comprises at least 110 VAC or 220 VAC . 24. A solid state light emitting device comprising: a rectifier circuit configured to be coupled to an AC voltage source to provide a rectified AC voltage; a series-connected string of LED groups coupled to the output of the rectifier circuit without a switched-mode power supply coupled between the output of the rectifier circuit and the series-connected string of LED groups; at least one capacitor coupled to the output of the rectifier circuit; a current limiter circuit, including a current mirror circuit, configured to limit current through at least one of said groups of LEDs to less than a current produced by said rectifier circuit and responsive to a rectified AC voltage applied to an input of said rectifier circuit , selectively charging and discharging said at least one capacitor via said rectifier circuit and via at least one of said LED groups; a plurality of current shunt circuits coupled to respective nodes between the LEDs in the string and configured to selectively enable and disabled; and a substrate having first and second opposing surfaces, wherein at least said string of series-connected LED groups, said plurality of current shunt circuits, said current limiter circuit and said rectifier circuit are mounted on either the first or second On the contrary surface, wherein said string of series-connected LED groups is arranged in an LED portion of said first or second opposing surface, said LED portion comprising an LED area occupying 40% or less of said first or second opposing surface , wherein a plurality of said strings of series-connected LED groups are configured to emit light comprising 800 lumens or more. 25. The apparatus of claim 24, wherein each of said plurality of current shunt circuits comprises: a transistor providing a controllable current path between the first node of the string and a terminal of the rectifier circuit; and A shutdown circuit is coupled to the second node of the string and the control terminal of the transistor and configured to control the current path in response to a control input. 26. The apparatus of claim 24, wherein the LEDs in the string comprise chip-on-board LEDs mounted on the substrate. 27. The device of claim 24, wherein the substrate comprises a flexible circuit board, the device further comprising: A heat sink, mounted on the base, is opposite and adjacent to the string of LED groups. 28. The apparatus of claim 24, wherein the substrate comprises a metal base printed circuit board MCPCB. 29. The apparatus of claim 28, wherein the MCPCB comprises a metal layer separated from the surface of the substrate by an insulating layer and configured to conduct heat away from the string of LED groups. 30. The apparatus of claim 24, wherein the substrate comprises a flexible printed circuit board. 31. The apparatus of claim 24, wherein at least said plurality of current shunt circuits comprise discrete electronic component packages mounted on said substrate. 32. The apparatus of claim 24, wherein said string of series-connected LED groups comprises at least three groups coupled in series with each other, each of said three groups comprising at least two chip-on-boards coupled in parallel with each other High voltage LEDs. 33. The apparatus of claim 24, wherein said AC voltage source input comprises at least 110 VAC. 34. The apparatus of claim 24, wherein said string of series-connected LED groups comprises at least three groups coupled in series to each other, each of said three groups comprising at least two high voltage boards coupled in series to each other Chip LEDs. 35. The apparatus of claim 24, wherein said AC voltage source input comprises at least 220 VAC. 36. The apparatus of claim 24, wherein at least one of said strings of series LED groups comprises at least two high voltage chip-on-board LEDs coupled in parallel or in series with each other, and said AC voltage source comprises at least 110 VAC or 220 VAC. 37. A printed circuit board PCB comprising: a substrate configured to be included in a solid state lighting housing, the substrate having first and second opposing surfaces, at least one of the opposing surfaces configured to mount a plurality of chip-on-board light-emitting diodes (LEDs) thereon, and the substrate being configured to be coupled to an AC voltage source input from outside the solid state lighting housing without coupling a switched mode power supply between the AC voltage source input and the plurality of chip-on-board LEDs, and configured to Mounted thereon are a plurality of discrete current shunt circuit devices coupled to respective nodes between several of said LEDs and configured to respond to changes in magnitude with a rectified AC voltage supplied to said LEDs. The bias state transition of the set of LEDs is selectively enabled and disabled, wherein the plurality of chip-on-board LEDs are disposed in an LED portion of the first or second opposing surface of the substrate, the LED portion comprising Occupying 40% or less of the LED area of the first or second opposing surface, wherein the plurality of chip-on-board LEDs are configured to emit light comprising 800 lumens or more. 38. The PCB of claim 37, wherein the substrate comprises a metal-based PCB. 39. The PCB according to claim 38, wherein said first opposing surface comprises a conductive circuit pattern layer and said second opposing surface comprises a base metal layer having a thickness greater than said conductive circuit pattern layer, said PCB further comprising said conductive circuit pattern layer An insulating layer between the conductive circuit pattern layer and the basic metal layer. 40. The PCB of claim 37, wherein the substrate comprises a flexible PCB. 41. The PCB according to claim 40, further comprising: The thermally conductive fillets in the base are located at specific locations opposite the locations on which the strings of chip-on-board LED sets are to be mounted. 42. The PCB of claim 37, further comprising: an encapsulant barrier, protruding from the surface at least partially surrounding a location on the surface where at least one of the LEDs are to be mounted, configured to reduce flow of encapsulant material away from the LED during application of the encapsulant material, to Formation of a lens on at least one of said LEDs is facilitated.