LED package and the process making the same

Details LED package and the process making the same LED package and the process making the same

2002-10-04

2004-08-03

Crane, Sara (Department: 2811)

Semiconductor device manufacturing: process

Making device or circuit emissive of nonelectrical signal

Packaging or treatment of packaged semiconductor

C438S029000

Reexamination Certificate

active

06770498

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to photoelectric semiconductor, and more particularly to a process for fabricating a light emitting diode (LED) package and the structure of the LED package.
BACKGROUND OF THE INVENTION
A conventional lamp-typed LED package is made by the following process. Firstly, provide a frame made of an electrically conductive metal. The frame has a numbers of pairs of leads arranged parallel and interconnected with each others through a cross bar. Each pair of leads is served as a positive pole and a negative pole of one LED package. On one of the poles, generally the negative pole, a bowl-shaped recess defining a reflecting surface for reflecting light is formed. Next, an LED die is attached on a bottom of the bawl-shaped recess of each negative pole by an electrically conductive adhesive, e.g. silver adhesive, such that an N-electrode of the LED die is electrically connected to the negative pole. Then, a P-electrode of each LED die is electrically connected to the other lead, i.e. the positive pole, through a gold wire by wire-bonding technique. By means of a molding technique, the LED dies are then respectively encased by a dome-shaped epoxy resin encapsulant with the metallic leads partially projecting out of the respective encapsulant and the cross bar is exposed outside the encapsulants. Finally, the cross bar is cut to obtain a numbers of LED packages.
Compared with other lighting devices, such as fluorescent lamps and incandescent lamps, the heat emitted by the LED package is low, but a certain amount of the heat, which is generated while the LED die glows by the electricity of from tens to hundreds of milliamperes, is a major factor resulted in the damage of the LED package. Accordingly, the present research and improvement is also focused on reducing the heat generated by the LED die. As far as the foregoing prior art LED package is concerned, the die is encapsulated in the epoxy encapsulant, which thermal conductivity is poor, and the contact area between the die and one of the leads is small. Besides, a protrudent portion of the leads out of the encapsulant is in the shape of a thin bar, so that the thermal conductivity of the above-mentioned conventional LED package is very poor and further improvement is required.
SUMMARY OF THE INVENTION
The primary objective of the present invention is to provide a process for fabricating LED packages, whereby a better thermally conductive and durable LED packages are made.
To achieve the foregoing objective of the present invention, the process for fabricating LED packages involves the following steps. Step A: Provide a platelike frame made of an electrically conductive metal. The frame has a plurality of cells, each of which includes a main plate and a separate arm, and no connection but a space between the main plate and the separate arm. Step B: Attach an LED die on a top surface of each main plate of the frame so as to electrically connect an electrode on a bottom side of the die to the main plate. Moreover, form a reflecting ring on each main plate with a molding technique, wherein the reflecting ring is made of opaque white plastic and has an upward sloping inner surface, and the die is positioned in the center of the reflecting ring. Step C: Connect the other electrode on a top surface of the die to a top surface of the separate arm with a conductive wire by means of wire bonding technique. Step D: Form an encapsulant on each cell of the frame with epoxy resin by means of the molding technique, wherein the encapsulant encapsulates the die, the reflecting ring and the conductive wire, and covers the main plate and the separate arm and also fills the space between the main plate and the separate arm to remain their spaced apart in opposite relationship. Additionally, the encapsulant has a top domelike protrusion. Step E: Cut the platelike frame substantially according to the size of each of the cells such that a plurality of LED packages are made.


REFERENCES:
patent: 5698866 (1997-12-01), Doiron et al.
patent: 6670648 (2003-12-01), Isokawa et al.
patent: 6707069 (2004-03-01), Song et al.

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