Patent Application
20080042157
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve for explaining the principles of the invention.
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After the LED chip 220 with the leadframe 210 are joined, an encapsulant 240 is formed on the LED chip 220 and a part of the leadframe 210 in the present embodiment for encapsulating the LED chip 220 and the part of the leadframe 210. The method for encapsulating the LED chip 220 and the part of the leadframe 210 is, for example, a dispensing process. Except for the dispensing process, a molding technology or other appropriate technologies can be also used in the present invention to achieve the purpose of encapsulating the LED chip 220 and the part of the leadframe 210. In this way, the LED chip 220 is able to be avoided from damage by an external force or from dust pollution.
In an embodiment of the present invention, the encapsulant 240 is, for example, a transparent encapsulant, such as silicone resin, to facilitate the light emitted from the LED chip 220 to propagate to the outside environment in more amount. Note that the present invention does not limit the color of the encapsulant 240, i.e. the encapsulant 240 can have any color, which determines the color the LED package appears during an operation.
In an embodiment of the present invention, an LED chip producing ultraviolet light can be used, wherein red fluorescence powder, green fluorescence powder or blue fluorescence powder is mixed into the encapsulant 240, so that the LED package is able to transmit red light, green light, or blue light, respectively. In addition, a combination in an appropriate proportion of red fluorescence powder, green fluorescence powder and blue fluorescence powder can be used in the present invention as well to make an LED package produce white light.
In another embodiment of the present invention, an LED chip producing blue light with the encapsulant 240 mixed with yellow fluorescence powder can be used to make the LED package produce white light. In more detail, under the combination of the blue light LED chip and the yellow fluorescence powder, the yellow fluorescence powder is irradiated by the blue light transmitted from the blue light LED chip and then produces yellow light, further the produced yellow light and the blue light are light interfused and consequently produce white light. However, the present invention does not limit the color of the light produced by the surface mount LED package. A manufacturer can select a desired fluorescence powder for adding into the encapsulant to meet the design requirement.
Accordingly, for advancing the luminous efficiency of a surface mount LED package, the leadframe can have a metal plating film (not shown), which is formed on the leadframe by using, for example, a plating process. The material of the metal layer can be silver to make the metal layer have good light reflectivity. In other words, in this way, the light transmitted from the LED chip can be reflected to the outside environment in more amount by the metal layer and the luminescence efficiency of the surface mount LED package is accordingly advanced.
In summary, the present invention adopts a flip chip technology to electrically connect an LED chip to a leadframe. Compared with the prior art, where the luminescence efficiency of a surface mount LED package is affected by the lower light reflectivity of the die bonding adhesive; or a part of the light transmitted from a LED chip is hidden by the bonding wires thereof, thus, the light transmitted from an LED chip of the present invention can travel to the outside environment in more amount. Hence, the luminescence efficiency of the surface mount LED package is advanced.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the specification and examples to be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims and their equivalents.
