Patent Application
20110241059
1. Field of the Invention
The invention relates to an LED die structure and a method for manufacturing the bottom terminal thereof, and more particularly to a bottom terminal consisting of a bottom and side terminal that ensures a stable quality of the electric connection when applied to a vertically conducted type LED packaging/assembly arrangement.
2. Description of the Related Art
Light-emitting diodes (LED) have a small size and a high luminous efficiency. Moreover, they are able to emit a light having different colors, thereby ensuring a various application. As a result, a lot of packaging (assembly) shapes has been created. The packaged products are generally known as lamps or SMD (surface mounting device). Apart from the appearance, another important consideration point is the quality reliability. Therefore, the die bonding is an important step for both the lamp arrangement and the SMD-arrangement before or after the packaging process. The term “die bonding” refers to a process in which an LED die is sucked, adhered or clamped first, and then placed on a solid lead frame coated with sticky and liquid plastic material. Meanwhile, a certain pressure is applied to ensure a firm attachment of the bottom of the LED die to the liquid plastic material. Thereafter, a heating process is carried out to solidify the plastic material, thereby completing the die bonding process.
The lead frame is made of metal material or coated with a solid material (such as metal film). The selection of the metal material lies in that the metal material features an easy processing and an excellent heat-dissipation. Particularly, the electric conductivity is necessary for some LED dies. For example, the electric current of the vertical LED flows in from the upper terminal pad and passes vertically through the die. Finally, it flows out from the bottom. The package has to employ the lead frame having the electric conductivity. The silver paste is a widely used die-bonding paste. Apart from the viscosity and the fluidity, the silver paste also has the electric conductivity due to the incorporation of silver powder. As a result, the combination of the vertical die, the die-bonding paste and the conductive lead frame creates a top-bottom current path. Such structural design is commonly found in LED components made of quaternary materials, and has become heavily commercialized.
As shown in
However, it is apparent from the cross-sectional view of the die-bonding structure in
An object of the invention is to provide an LED die structure and a method for manufacturing the bottom terminal thereof that enhances the quality of the electric connection between the die-bonding paste and the LED die.
In order to achieve the above-mentioned object, the invention includes:
a) a substrate;
b) a light-emitting layer positioned at the top of the substrate;
c) at least one bottom terminal positioned at the bottom of the substrate;
d) at least one top terminal positioned at the top of the light-emitting layer; and
e) at least one side terminal positioned at the side of the bottom of the substrate.
According to the invention, the height of the side terminal is adapted to the height of the die-bonding paste for the packaging process. The die-bonding paste comprises silver paste. The material for the substrate is selected from a group, consisting of Si, Ge, GaAs, and GaP.
According to the invention, a method for manufacturing the bottom terminal of the LED die structure, wherein the method comprises the following steps:
a) recessing the bottom side of the wafer to a predetermined height when the LED is formed in a wafer type;
b) coating the metal material to the bottom of the wafer and to the inside of the recesses (by use of the metal coating process); and
c) dividing the wafer along the recesses into dies,
whereby the bottom terminal and the side terminal are formed at the bottom of the substrate of the die.
According to the invention, another method for manufacturing the bottom terminal of the LED die structure, wherein the method comprises the following steps:
a) dividing the LED wafer into dies; and
b) coating the metal material to the bottom and the sides of the dies (by use of the metal coating process),
whereby the bottom terminal and the side terminal are formed at the bottom of the substrate of the die.
The accomplishment of this and other objects of the invention will become apparent from the following descriptions and its accompanying figures of which:
First of all, referring to
According to the invention, the LED die structure improves the design of the terminal. In addition to the bottom terminal 43 and the top terminal 44, a side terminal 45 with a predetermined height is provided at the bottom of the substrate 41. After the packaging process, the lead 31 electrically connects the top terminal 44 and the second lead frame 30b, while the bottom terminal 43, the side terminal 45, and the second lead frame 30b are electrically connected by the die-bonding paste 20. When a bad contact takes place between the bottom terminal 43 of the die and the die-bonding paste 20, an instable electric connection may be avoided by the good connection of the side terminal 45 with the side wall of the die-bonding paste 20.
The material suitable for the substrate 41 may be Si, Ge, GaAs, or GaP. The bottom terminal 43 and the side terminal 45 may be formed by the metal coating process. The height of the side terminal 45 is adapted to the height of the die-bonding paste 20 for the packaging process. Moreover, the die-bonding paste 20 is the silver paste.
As shown in
Recessing the bottom side of the wafer to a predetermined height when the LED is formed in a wafer type;
Coating the metal material to the bottom of the wafer and the sides of the recesses (by use of the metal coating process having the coverage effect); and
Dividing the wafer along the recesses into dies by use of the cutting or breakup process.
In this way, the bottom terminal 43 and the side terminal 45 are positioned at the bottom of the substrate of the die.
As shown in
Dividing the LED (in shape of wafer) into dies by use of the cutting or breakup process;
Coating the metal material to the bottom and the sides of the dies (by use of the metal coating process having the coverage effect); and
In this way, the bottom terminal 43 and the side terminal 45 are positioned at the bottom of the substrate of the die.
Many changes and modifications in the above-described embodiments of the invention can, of course, be carried out without departing from the scope thereof. Accordingly, to promote the progress in science and the useful arts, the invention is disclosed and is intended to be limited only by the scope of the appended claims.
