Patent Application
20070246717
This invention relates to light sources and more specifically to light sources that are both thermally and space efficient.
Prior art light sources, such as light emitting diode (LED) light sources, typically have an LED chip attached to a printed circuit board (PCB). A wire connection is made between the LED chip and the PCB substrate. The assembly is then encapsulated with a light transparent material, such as clear epoxy. This arrangement suffers from two disadvantages, namely, the package is thick (on the order of 0.25 to 1.0 mm and has relatively low heat dissipation from the LED through the PCB.
Prior attempts to correct the thermal transfer problems have been to increase the thickness of the plating that is used to electronically connect the LCD chip. However there is a limit as to how much the plating can be increased. The thickness (space) issue has been addressed by reducing the thickness of the substrate. Here again, there is a limit as to how thin the PCB can be made. Usually it is not practical to reduce the PCB to less than 0.15 mm in thickness.
A light source that is both thermally and spatially efficient can be achieved by attaching a light source, such as an LED chip, to a flexible circuit and positioning a light conductive material around the light source. For one embodiment, a cavity is created around the light source such that the light conductive material, for example, clear silicone, can be positioned within the cavity. In one embodiment, the cavity is created by a housing, such as a premolded plastic housing, secured to the flexible circuit. In one embodiment, a lens can be secured to the device to form the light.
Housing 12 could be, for example, molded using plastic or any other desired material. Encapsulant 16 could fill cavity 13 forming a top surface that is plumb with the top surface of housing 12 or the encapsulant could, for example, fill less than the entire cavity and be formed, if desired, into a lens. The encapsulant protects the light source from the external environment. In some situations, the encapsulant material can be used to support the light source and/or to form a pocket to house a lens.
The flexible circuit can be made relatively thin, for example, having 0.1 mm of thickness or less. Since the flexible circuit is thin (providing space efficiency), heat is more easily conducted through the flexible circuit and away from LED chip 14, thereby providing increased thermal efficiency.
In process 303, the housing is then attached (by gluing or otherwise) to the flexible circuit. The housing either has cavity 13 (
In process 305, optional lens can be placed on the top of (or within or partially within) the cavity. Note that the lens can be added after the encapsulant support material is in position, or the lens can be integral with the housing. If the lens is added integral to the housing, the uncured silicone could be inserted through the housing (perhaps through a sealable hole) after the housing is mated to the substrate. Also, the encapsulant can be premolded into the housing in some situations.
Encapsulant 16 (in this embodiment as well as in the other embodiments shown) can be loaded with a color shifting material, for example, phosphor, such that colored light different from that emitted by the LED can be obtained. For example, white light can be obtained by combining a blue LED and yellow phosphor materials.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
