Patent Application
20050213334
The present invention relates to packaging technologies. More specifically, the present invention relates to packaging for light emitting diodes (LEDs).
Light emission diode packages (“LED packages”) are semiconductor devices, which have LED chips acting as light sources. LEDs comprise compound semiconductor materials that produce light when electrically activated. Some examples of some compound semiconductor materials are GaAs, AlGaAs, GaN, InGaN and AlGaInP,
As an LED converts electric energy into light, it is highly efficient and far more durable, and consumes much less electricity than filament bulbs. As the practical use of LEDs gains momentum, they are becoming more widely used in displays such as the indicators for electrical appliances and the backlights for liquid crystal displays in cellular phones.
Conventional LED packages are made of plastic to keep component size and cost down. The plastic shell houses one or more LEDs and is then filled with an optically transparent material to seal and protect the LED from the environment.
One problem associated with conventional plastic LED packages is light leakage. To help make smaller LED packages, the thickness of the plastic package is reduced. As a result, the thinner packaging of the LED allows light leakage through the LED package. Light leakage makes the LED device less efficient, thus requiring more power to achieve a desired brightness, resulting in more power consumption of the device it is in. In addition, as electronic devices become smaller, LEDs must also be smaller. As a result, the smaller LED package has problems with dissipating the heat that is generated by high brightness LEDs.
Embodiments of the present invention include a light emitting diode package comprising a ceramic cavity comprising a substrate for mounting a light emitting diode and substantially vertical sidewalls for reducing light leakage. In one embodiment, the opaque nature of the ceramic material and specifically the reflective plating that prevent light leakage. The ceramic LED package further includes a metallic coating on a portion of the ceramic substrate for reflecting light in a predetermined direction.
Embodiments of the invention also include a method for manufacture of a light emitting diode package comprising forming a ceramic cavity comprising a substrate for mounting a light emitting diode and substantially vertical sidewalls for reducing light leakage. The method further includes coating a portion of the ceramic cavity with a light reflective material, positioning a light emitting diode on the substrate and depositing an optically transparent material in the cavity to protect the light emitting diode.
Additional embodiments of the present invention include forming a one-piece substrate and cup LED package and forming the cup in different shapes to focus light in a predetermined direction. In other embodiments of the present invention, the vertical placement of an LED device in the cavity is adjusted to widen and narrow the viewing angle of the LED device. Furthermore, molded epoxy is deposited over the LED package in multiple arrangements to further direct the direction of light.
The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
Reference will now be made in detail to the various embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the various embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the invention as defined by the appended claims.
Furthermore, in the following detailed description of the invention, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be obvious to one skilled in the art that the invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the invention.
The present invention relates to the manufacture of a ceramic LED package. The exemplary ceramic LED package of the present invention has excellent thermal properties and endurance to withstand heat from a high brightness LED device contrary to conventional plastic LED packages. The thermal properties of the ceramic package allow improvement in the brightness of LEDs without the requirement of making the package resistant to additional heat produced and without equipping the package with means for dissipating the heat quickly. The use of alumina and or aluminum nitride ceramic materials makes the ceramic LED package less susceptible to the degrading heat generated by high brightness LED devices. In addition, the ceramic package retains more light and does not allow light leakage as do conventional resin based LED packages. Such ceramic package also allows the use of high temperature during the assembly processes.
Ceramic LED packages can be made in smaller dimensions than conventional resin based LED packages and manufacturing techniques allow the sidewalls of the ceramic LED package to be formed substantially vertical, thus increasing the surface area of the ceramic cavity and allowing multiple LED devices to be mounted in a single ceramic LED package. The use of ceramic provides a more electrically efficient LED device that can be made smaller and at a lower cost.
Embodiments of the present invention are related to packaging for high brightness LED devices. In one embodiment of the invention, a ceramic substrate is used to reduce light leakage in a high brightness LED to improve efficiency of the LED. Reducing the amount of light leakage reduces the amount of power required to achieve a desired brightness. In addition to a ceramic package substrate, embodiments of the present invention provide a ceramic LED package that is coated with a light reflective material to further increase light intensity and to further reduce light leakage.
In one embodiment of the present invention, ceramic package 100 comprises electrical connections 140 to electrically couple LED 130 to a first portion of metal routing 132 on the inside of the ceramic package and the outside of the ceramic package. In addition, a wire bond 125 can be used to electrically couple LED 130 to a second portion of metal routing 132.
The present invention provides a ceramic LED packaging to reduce light leakage of a high brightness LED. In addition to reducing light leakage, a ceramic package allows the dimensions of the package to be scaled down. In accordance with embodiments of the present invention, a ceramic LED package can be made in smaller dimensions than a conventional plastic LED package. In addition, the contour of the sidewalls of the ceramic package can be manufactured such that the sidewalls are substantially vertical. In a conventional LED package, the sidewalls are not vertical (e.g., slopping from the top of the package to the bottom of the package) because the manufacture of plastic LED packages produces sidewalls that are not vertical, thus reducing the area on the bottom of the package. In one embodiment of the present invention, the ceramic LED package comprises vertical sidewalls, thus increasing the surface area of the bottom of the package given a particular device dimension.
In one embodiment of the present invention, the ceramic LED package 110 is plated with metal to form a light reflective coating on the inner surface of the ceramic package 110. In one embodiment of the invention, the metallic plating is silver, but the plating can be any light reflective material that can be deposited on the surface of the ceramic package 110. In one embodiment of the invention, silver is electro plated on the surface of the ceramic package. It is appreciated that any process well known can be used to coat the ceramic package 110 with the light reflective material 120.
In one embodiment of the invention, the light reflective material is formed in specific locations to reflect light in a predetermined direction. As such, these locations may not be electrically connected to the metal routing 132.
In one embodiment of the invention, multiple ceramic packages 110 are formed in sheets wherein multiple ceramic packages are formed at once. In one embodiment, the ceramic packages are formed using a die that can be stamped on a sheet of ceramic material to form the ceramic LED package 110. In accordance with the present invention, the sidewalls of the ceramic package 110 are substantially vertical, thus providing maximum surface area on the bottom of the ceramic package 110 for mounting multiple LED devices. By using ceramic material to form the package 110, the dimensions of the package can be smaller than conventional LED packages, thus reducing the footprint of a device that achieves a desired brightness level. Step 302 of
In one preferred embodiment of the present invention, the light reflective coating is metallic and is electro plated on the ceramic LED package 110. In one embodiment of the invention, the light reflective coating 120 is an opaque metallic coating. The light reflective coating increases the total light intensity and flux the LED. In addition, the light from the LED can be focused in a predetermined location thus further increasing the efficiency of the device in a specific direction.
As illustrated in
After the LED is positioned in the ceramic LED package, the next step of exemplary process 300 of
Additional embodiments of the present invention include a one-piece ceramic package comprising a substrate and an embedded reflector cup in accordance with embodiments of the present invention. In one embodiment of the invention, the shape of the reflector cup is modified to focus light in a desired location. In other embodiments of the present invention, a reflective material, such as silver or gold, can be disposed on the walls of the reflector cup to further enhance the brightness of the device. Furthermore, epoxy resin can be deposited in the reflector cup and over the LED to protect the LED. In one embodiment of the invention, the epoxy is formed in a dome or concave over the LED to further control the viewing angle of the LED device. Additionally, the vertical location of the LED device, with respect to the bottom and top of the reflector cup, can be modified to change the viewing angle of the device.
In summary, the ceramic LED package has excellent thermal properties and endurance to withstand heat from a high brightness LED device contrary to conventional plastic LED packages. The thermal properties of the ceramic package allow improvement in the brightness of LEDs without the requirement of making the package resistant to additional heat produced and without equipping the package with means for dissipating the heat quickly. The use of alumina and or aluminum nitride ceramic materials makes the ceramic LED package less susceptible to the degrading heat generated by high brightness LED devices. Such ceramic package also allows the use of high temperature during the assembly processes. In addition, the ceramic package retains more light and does not allow light leakage as do conventional resin based LED packages.
Ceramic LED packages can be made in smaller dimensions than conventional resin based LED packages and manufacturing techniques allow the sidewalls of the ceramic LED package to be formed substantially vertical, thus increasing the surface area of the ceramic cavity and allowing multiple LED devices to be mounted in a single ceramic LED package. The use of ceramic provides a more electrically efficient LED device that can be made smaller and at a lower cost.
Embodiments of the present invention, ceramic package for high brightness LED devices has been described. While the present invention has been described in particular embodiments, it should be appreciated that the present invention should not be construed as limited by such embodiments, but rather construed according to the following claims.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.
