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Typically, there are provided wire connects between an electrode on each one of LED dice 15 and bonding pads on substrate 20. On an outer surface of walls 25, electrodes may be electrically connected to a motherboard, and the pathway from the motherboard through the electrodes supplies electrical current to the LED dice 15. The number of LED dice 15 depends on the design of substrate 20 and light guide 10.
For side-emitting LED dice 15 used as a light source for light guide 10, LED package 5 is normally located very close to light guide 10 in order to avoid light loss between LED package 5 and light guide 10.
Normally, side emitting LED package 5 is designed to deliver as much light as possible to light guide 10. A convex lens may be mounted on the outer surface of the encapsulate material, and outside of aperture 40, to collimate light into a direction toward light guide 10. However, the configuration with the convex lens mounted on the outer surface of the encapsulate material is generally not recommended because some light goes through a side area of the convex lens and never goes into light guide 10.
Typically, LED package 5 contains red, green and blue (RGB) LED dice 15 in elongate cavity 30. Using RGB LED dice 15 as the light source for the backlight of light guide 10 into the LCD generally provides a wide color range, but requires an area for color mixing. If color mixing is accomplished inside of LED package 5, which generates mostly white light, light guide 10 will generally require a smaller area for color mixing. Controlling light from LED dice 15 in elongate cavity 30 is limited without the use of a convex lens outside of aperture 40, on encapsulation material 35.
A reflector cup within elongate cavity 30 may be provided in order to provide good color mixing without the use of a lens. The reflector cup acts to control the direction of light from one or more of LED dice 15. However, the reflector cup only controls the direction of light from the side of a die and does not control the direction of reflected light traveling in a direction from the top of the die through aperture 40.
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In an embodiment, there is provided an opto-electronic package comprising a substrate having a base and a plurality of cavity-defining walls, the base and the plurality of cavity-defining walls defining an elongate cavity having a major axis, a minor axis and an aperture, and the base having a surface that presents within the cavity; a plurality of light emitting diode (LED) dice mounted to the surface of the base that presents within the elongate cavity of the substrate so as to project light within the elongate cavity; and at least one lens disposed between the cavity-defining walls and having a maximum height remaining within the aperture of the elongate cavity, and the at least one lens having a convex orientation relative to at least one of the plurality of light emitting diode (LED) dice along the minor axis of the elongate cavity of the substrate.
In another embodiment, there is provided a system for backlighting an LCD screen, the system comprising an opto-electronic package, comprising a substrate having a base and a plurality of cavity-defining walls, the base and the plurality of cavity-defining walls defining an elongate cavity having a major axis, a minor axis and an aperture, and the base having a surface that presents within the cavity; a plurality of light emitting diode (LED) dice mounted to the surface of the base that presents within the elongate cavity of the substrate so as to project light within the elongate cavity; and at least one lens disposed between the cavity-defining walls and having a maximum height remaining within the aperture of the elongate cavity, and the at least one lens having a convex orientation relative to at least one of the light emitting diode (LED) dice along the minor axis of the elongate cavity of the substrate; a light guide having an input portion and an output portion, the input portion operatively associated with the aperture to receive light provided by the plurality of light emitting dice (LED) dice, and the output portion operatively associated with the LCD screen to transmit the light from the input portion to the LCD screen.
In another embodiment, there is provided a method of manufacturing an opto-electronic package, comprising fabricating a substrate having a base and a plurality of cavity-defining walls, the base and the plurality of cavity-defining walls defining an elongate cavity having a major axis and an aperture, the base having a surface that presents within the cavity; attaching a plurality of light emitting diode (LED) dice to the base of the substrate within the cavity; and disposing at least one lens between the cavity-defining walls and entirely within the aperture of the elongate cavity, and the at least one lens having a convex orientation relative to at least one of the plurality of light emitting diode (LED) dice along the minor axis of the elongate cavity of the substrate.
Other embodiments are also disclosed.
Illustrative embodiments of the invention are illustrated in the drawings, in which:
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In an embodiment, plurality of lens portions 215 each comprise plastic lens 200 disposed over light emitting diode (LED) 110 within elongated cavity 130. In one embodiment, encapsulation material 195 is disposed over light emitting diode (LED) 110 and within plastic lens 200. In an embodiment, encapsulation material 195 may comprise epoxy. In another embodiment, encapsulation material 195 may comprise silicone.
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In an embodiment, a jig 250 is selectively disposed within elongate cavity 130 for casting encapsulation material 195 so as to form one or more of the at least one lens 115.
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In an embodiment, there is provided a method of manufacturing an opto-electronic package. Generally, the method comprises fabricating a substrate having a base and a plurality of cavity-defining walls, the base and the plurality of cavity-defining walls defining an elongate cavity having a major axis and an aperture, the base having a surface that presents within the cavity. The method comprises attaching a plurality of light emitting diode (LED) dice to the base of the substrate within the cavity. The method comprises disposing at least one lens between the cavity-defining walls and entirely within the aperture of the elongate cavity, and the at least one lens having a convex orientation relative to at least one of the plurality of light emitting diode (LED) dice along the minor axis of the elongate cavity of the substrate.
In one embodiment, the method may comprise disposing the at least one lens between the cavity-defining walls and entirely within the aperture comprises disposing an encapsulation material over the plurality of light emitting diode (LED) dice within the elongated cavity, and curing the encapsulation material so as to form the at least one lens with the encapsulation material.
In relation to the step of disposing the at least one lens between the cavity-defining walls and entirely within the aperture comprises disposing a plastic lens over the plurality of light emitting diode (LED) dice within the elongated cavity, the method may comprise disposing an encapsulation material within the plastic lens and over the plurality of light emitting diode (LED) dice, and curing the encapsulation material so as to form the at least one lens with the plastic lens and the encapsulation material.
In relation to the step of disposing a jig through the aperture into the elongated cavity and over the plurality of light emitting diode (LED) dice, the method may comprise disposing an encapsulation material within the jig and over the plurality of light emitting diode (LED) dice, curing the encapsulation material so as to form the at least one lens with the encapsulation material, and removing the jig from the elongated cavity through the aperture.
The method may further comprise positioning the substrate to align the major axis in a vertical direction, and disposing the encapsulation material through a first hole defined in the first end into the elongated cavity within the jig and over the plurality of light emitting diode (LED) dice.
In one embodiment, lens 115 is created inside of elongate cavity 130, and the top of lens 115 does not extend from package 100. One convex lens 205 is applied to one die 110, and a curvature of lens 205 may be designed for each differing type of die 110.
For the horizontal direction parallel to major axis 175, light from LED die 110 spreads out and mixes with light from an adjacent die 115 in order to improve color mixing. For the vertical direction parallel to minor axis 180, light from LED die 110 focuses toward the central axis of light guide 140 for an increase in luminous intensity. In order to optimize color mixing and intensity, curvature for in the horizontal direction and in the vertical direction may be different from one another. A suitably sized aspherical oval lens may be used.
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In order to maximize the effect of lens, the lens may be located at a far distance from the light source LED die, and the size of the lens may be sized relatively large in comparison to the size of the light source. However, the LED die size cannot be sized too small in order to maintain adequate brightness, and the aperture of the housing is normally limited at the width of the light guide for good light coupling. Within these constraints, the top of the lens may be located at the same position as the edge of the housing, and the size of the lens may be sized as large as possible within the aperture size of the substrate.
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In an embodiment, the substrate may be made of plastic or ceramics, and some pieces may be built on one sheet of plastic or ceramics in an array. Bond pads and electrodes may be made on the substrate using, for example, plating techniques on plastic or a known via hole techniques on ceramics. After attaching LED dice and connecting the die and wire bond pad with a gold wire, encapsulate material may be disposed into elongate cavity.
A jig which has a concave cavity may be used to create the convex lens shape on the encapsulate material during a process of curing the encapsulate material.
In an embodiment, the jig is attached on the housing prior to placement of the encapsulate material. The jig is preferably inserted into the elongate cavity and fixed into position along the wall of the substrate. In order to optimize alignment of the lens position to the die position, the jig may be pressed towards the housing during the process of placing and curing the encapsulate material.
In order to avoid an air bubble from the encapsulate material, the substrate is preferably held vertically and the encapsulate material is added through a hole located at a bottom position, and air is allowed to escape through another hole at a top position.
When the encapsulate material is fully filled, a residual amount of the material may escape the hole at the top position. This residual amount may remain at an outside area of the substrate. This residual amount may be removed by trimming after cure.
After curing the encapsulate material, the jig is removed, and each package is separated by sawing or snapping.
In an embodiment, convex lenses are fabricated as an array of plastic lenses separate from the package, and these pre-fabricated lenses are each subsequently attached to the substrate of the package. In an embodiment, after die attaching and wire bonding, a liquid type of transparent material is casted in the elongate cavity to cover the LED dice and wires. Before curing the transparent material, the plastic lenses of the array are attached inside of the substrate. The bottom surface of the lens may be either flat or convex shape to prevent an air bubble from being trapped under the bottom surface on top of the transparent material. Each of the lenses in the array may have a hole or a slit to allow escape of the residue of the transparent material. After attaching the lenses of the array, the transparent material may be cured in an oven.