Patent Application
20070272934
For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:
In accordance with the concepts set forth herein, a light-emitting diode (LED) device which has improved thermal properties over traditional LED designs is described. Embodiments of the present invention include a pre-compressed encapsulant with improved thermal properties, which at least partially surrounds or encapsulates a light-emitting diode. An hard outer shell is used in association with the pre-compressed encapsulant to enclose the compressible encapsulant and to ensure that the finished LED has the desired shape. A second encapsulant can also be used to seal the first encapsulant into the shell.
Referring to
LED chip 23 is placed in first encapsulant 22 and outer shell 21 to allow light produces by LED chip 23 to pass through first encapsulant 22 and outer shell 21. In the embodiment shown in
In certain embodiments, second encapsulant 24 is introduced into outer shell 21 in such a manner to allow it to pre-compresses first encapsulant 22 against the outer shell 21. This can be accomplished by first introducing the first encapsulant 22 into the outer shell 21 and curing the encapsulant 22. Outer shell 21 and first encapsulant 22 may then cooled to a temperature that results in the contraction of the first encapsulant 22. Once first encapsulant 22 has contracted, second encapsulant 24 is introduced into outer shell 21 so as to seal first encapsulant 22 into the outer shell 21. When the temperature of the LED is raised, for example to room temperature or above, first encapsulant 22 attempts to expand, pushing against outer shell 21 and second encapsulant 24. The first and second encapsulants should completely fill at least the closed portion of outer shell 21 to prevent air pockets from forming which might reduce the desired compression of first encapsulant 21. Because outer shell 21 and second encapsulant 24 are rigid and sufficiently bonded to each other, the first encapsulant becomes compressed.
The compression of the first encapsulant 22 described above is use to overcome traditional disadvantages of compressible materials such as silicone which can tend to delaminate from the walls of outer shell 21 during temperature excursions. By pre-compressing first encapsulant 22 in outer shell 21 the delamination effects can be reduced or eliminated.
In preferred embodiments, second encapsulant 24 is formed from a different material from first encapsulant 22, which can be a curable resin or other material which has the properties described herein. In the case of resin materials, the resin when cured, generally produces a material which is harder than the first encapsulant and preferably rigid in order to maintain the compression of first encapsulant 22. In certain embodiments, the second encapsulant may be an epoxy.
As described, preferred embodiments of outer shell 21 are formed from a material which is transparent at least to the wavelengths of light produced by LED chip 23, and possesses sufficient rigidity to retain its shape even when subject to the forces placed on it by compressed first encapsulant 22. Outer shell 21 can be of desired shape, color or configuration as required to provide an LED with the desired properties. In certain embodiments, outer shell 21 can be a light shaping structure such as dome 27 is shown in
As discussed above with reference to
In alternate embodiments, first encapsulant 22 may be sealed in outer shell 21 by other LED configurations, such as by LED 30 shown in
Referring now to
The pre-compressed encapsulant is then cured in process 44. In process 45, the outer shell containing the pre-compressed encapsulant and the LED chip is then cooled such that the cured first encapsulant contracts. This temperature is generally below room temperature. Once the first encapsulant has contracted, a second encapsulant is then layered on top of the first encapsulant such that the second encapsulant as shown by process 46. When cured, as shown by process 47, the second encapsulant seals the first encapsulant within the outer shell. In certain embodiments, the curing of the second encapsulant can be done by non-thermal methods, which do not raise the temperature of the first encapsulant. After curing the second encapsulant the finished LED can be allowed to warm to room temperature resulting in the first encapsulant expanding, or pressing against the outer shell and the second encapsulant
While the embodiment of method 40 shown in
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.
