Abstract:
LED dies are mounted a single submount tile (or wafer). The LED dies have a light emitting top surface. A uniformly thick layer of UV sensitive silicone infused with phosphor is then deposited over the tile, including over the tops and sides of the LED dies. Only the silicone/phosphor over the top and sides of the LED dies is desired, so the silicone/phosphor directly on the tile needs to be removed. The silicone/phosphor layer is then masked to expose the areas that are to remain to UV light, which creates a cross-linked silicone. The unexposed silicone/phosphor layer is then dissolved with a solvent and removed from the tile surface. The silicone/phosphor layer may be defined to expose a wire bond electrode on the LED dies. The tile is ultimately singulated to produce individual phosphor-converted LEDs.
Abstract:
After flip chip LEDs are mounted on a submount wafer and their growth substrates removed, a phosphor plate is affixed to the exposed top surface of each LED. A reflective material, such as silicone containing at least 5% TiO2 powder, by weight, is then spun over or molded over the wafer to cover the phosphor plates and the sides of the LEDs. The top surface of the reflective material is then etched using microbead blasting to expose the top of the phosphor plates and create a substantially planar reflective layer over the wafer surface. Lenses may then be formed over the LEDs. The wafer is then singulated. The reflective material reflects all side light back into the LED and phosphor plate so that virtually all light exits the top of the phosphor plate to improve the light emission characteristics.
Abstract:
In one embodiment, sub-micron size granules of TiO2, ZrO2, or other white colored non-phosphor inert granules are mixed with a silicone encapsulant and applied over an LED. In one experiment, the granules increased the light output of a GaN LED more than 5% when the inert material was between about 2.5-5% by weight of the encapsulant. Generally, a percentage of the inert material greater than 5% begins to reduce the light output. If the LED has a yellowish YAG phosphor coating, the white granules in the encapsulant make the LED appear whiter when the LED is in an off state, which is a more pleasing color when the LED is used as a white light flash in small cameras. The addition of the granules also reduces the variation of color temperature over the view angle and position over the LED, which is important for a camera flash and projection applications.
Abstract:
In one embodiment, sub-micron size granules of TiO2, ZrO2, or other white colored non-phosphor inert granules are mixed with a silicone encapsulant and applied over an LED. In one experiment, the granules increased the light output of a GaN LED more than 5% when the inert material was between about 2.5-5% by weight of the encapsulant. Generally, a percentage of the inert material greater than 5% begins to reduce the light output. If the LED has a yellowish YAG phosphor coating, the white granules in the encapsulant make the LED appear whiter when the LED is in an off state, which is a more pleasing color when the LED is used as a white light flash in small cameras. The addition of the granules also reduces the variation of color temperature over the view angle and position over the LED, which is important for a camera flash and projection applications.
Abstract:
A method according to embodiments of the invention includes positioning a flexible film (48) over a wafer of semiconductor light emitting devices, each semiconductor light emitting device including a semiconductor structure (13) including a light emitting layer sandwiched between an n-type region and a p-type region. The wafer of semiconductor light emitting devices is bonded to a substrate (50) via the flexible film (48). After bonding, the flexible film (48) is in direct contact with the semiconductor structures (13). The method further includes dividing the wafer after bonding the wafer to the substrate (50).
Abstract:
Optical elements (130) are attached to a support film (110) at select locations, the select locations corresponding to locations of light emitting elements (140) on another substrate, e.g. the substrate of the title (150).The film is placed on the substrate containing the light emitting elements such that the optical elements are in contact with their corresponding light emitting elements. The optical elements are laminated to the light emitting elements, and the support film is removed. The optical elements may include wavelength conversion elements, lens elements, combinations of elements, and so on. Other elements, such as conductors and reflectors may also be positioned on the laminate film
Abstract:
An underfill formation technique for LEDs molds a reflective underfill material to encapsulate LED dies mounted on a submount wafer while forming a reflective layer of the underfill material over the submount wafer. The underfill material is then hardened, such as by curing. The cured underfill material over the top of the LED dies is removed using microbead blasting while leaving the reflective layer over the submount surface. The exposed growth substrate is then removed from all the LED dies, and a phosphor layer is molded over the exposed LED surface. A lens is then molded over the LEDs and over a portion of the reflective layer. The submount wafer is then singulated. The reflective layer increases the efficiency of the LED device by reducing light absorption by the submount without any additional processing steps.
Abstract:
An underfill technique for LEDs uses compression molding to simultaneously encapsulate an array of flip-chip LED dies mounted on a submount wafer. The molding process causes liquid underfill material (or a softened underfill material) to fill the gap between the LED dies and the submount wafer. The underfill material is then hardened, such as by curing. The cured underfill material over the top and sides of the LED dies is removed using microbead blasting. The exposed growth substrate is then removed from all the LED dies by laser lift-off, and the underfill supports the brittle epitaxial layers of each LED die during the lift-off process. The submount wafer is then singulated. This wafer-level processing of many LEDs simultaneously greatly reduces fabrication time, and a wide variety of materials may be used for the underfill since a wide range of viscosities is tolerable.
Abstract:
Lenses and certain fabrication techniques are described. A wide-emitting lens refracts light emitted by an LED die to cause a peak intensity to occur within 50-80 degrees off the center axis and an intensity along the center axis to be between 5% and 33% of the peak intensity. The lens is particularly useful in a LCD backlighting application. In one embodiment, the lens is affixed to the backplane on which the LED die is mounted and surrounds the LED die. The lens has a hollow portion that forms an air gap between the LED die and the lens, where the light is bent towards the sides both at the air gap interface and the outer lens surface interface. The lens may be a secondary lens surrounding an interior lens molded directly over the LED die.
Abstract:
A flexible film comprising a wavelength converting material is positioned over a light source. The flexible film is conformed to a predetermined shape. In some embodiments, the light source is a light emitting diode mounted on a support substrate. The diode is aligned with an indentation in a mold such that the flexible film is disposed between the support substrate and the mold. Transparent molding material is disposed between the support substrate and the mold. The support substrate and the mold are pressed together to cause the molding material to fill the indentation. The flexible film conforms to the shape of the light source or the mold.