Patent Application
20050156177
The present invention is related to a light-emitting device, particularly to a light-emitting device having an enlarged area of active luminescence region so as to enhance the brightness, essentially providing a first connective circuit and a second connective circuit on a power supply substrate, without occupying the active luminescence region of the light-emitting device directly.
Light-emitting devices (LEDs) have been widely used in computer peripherals, communication products, and other electronic equipments owing to advantages, such as small volume, light weight, lower power consumption, and long service life, as examples. For general mass-produced LEDs, there is grown an epitxy layer with a PN junction on a substrate, made from the material such as sapphire, SiC, and so on. The light may be projected from the PN junction owing to the recombination of electron-hole, when a drive voltage is applied across two sides of the P-type epitaxy layer and the N-type epitaxy layer.
For a conventional LED device, as illustrated in
For a LED, the luminous flux is more, provided that the active area of the active luminescence region 153 is larger; while the luminous intensity is also higher, provided that the current flowing through the active luminescence region 153 is larger. If the current density flowing through the active luminescence region 153 is non-uniform, however, the appearance that the current density flowing through a part of active luminescence region 153 is too high, while the current density flowing through another part of active luminescence region 153 is relatively too low, may easily occur. When the current density flowing through the active illuminescense region 153 is so high to reach the saturation state, not only a reduced luminous yield, but also a locally raised working temperature in the active luminescence region 153, and even the damage may be effected. On the contrary, when the current density flowing through the active luminescence region is so low that the luminous yield could not be fully developed, the area of the element may be wasted. Therefore, how to facilitate the working current to flow through the active luminescence region 153 uniformly for enhancing the luminous yield is truly a significant problem in the fabrication and design for the LED.
It is extremely likely to bring about a non-uniform distribution of current density in the aforementioned structure of diode, however, owing to the geometrically asymmetrical distribution of the first electrode 17 and the second electrode 19. For the purpose of avoiding this non-uniform current density, a structure of LED enabling a uniform distribution of working current has been proposed by the industry. As illustrated in
Although the non-uniform distribution of the working current density in the active luminescence region 253 is effectively reduced by the use of aforementioned structure of LED, the zone of the LED 20 occupied by the second surface 255 is enlarged, reducing the active area of the active luminescence region 253, due to the fact that the second communicating electrode 293 is disposed on the second surfaces 255 of the second epitaxy layer 25 alternately, in other words, a part of second surfaces 255 should be further chiseled in order to accommodate the locations where the second communicating electrode 293 is disposed. Thereby, a part of area of the active luminescence region 253 may be occupied by the second communicating electrode 293, resulting in a regret of reducing the light output and brightness correspondingly.
For this purpose, how to design a novel light-emitting device with not only a relatively enlarged area of active luminescence region in a LED in order to enhance the brightness, but also an uniform distribution of working current density and thus a prolonged service life, aiming at the disadvantages in the above conventional technology, is the key point of the present invention.
Accordingly, it is the primary object of the present invention to provide a light-emitting device having an enlarged area of active luminescence region comprising a first connective circuit and a second connective circuit, provided on a power supply substrate, allowed for being electrically communicated to a plurality of corresponding first electrodes and second electrodes on a light-emitting diode (LED) die directly in place of a first communicating electrode and a second communicating electrode originally provided on the LED die, in order to avoid an area of the active luminescence region occupied by the first communicating electrode and the second communicating electrode, further resulting in the effect of relatively enhancing the luminous flux and brightness.
It is the secondary object of the present invention to provide a light-emitting device having an enlarged area of active luminescence region comprising a plurality of first electrodes and second electrodes designed such that the structure thereof is presented as geometrical symmetry, whereby the current density in the active luminescence region is uniformly distributed, further leading to an enhanced luminous yield and a prolonged service life of the product.
It is another object of the present invention to provide a light-emitting device having an enlarged area of active luminescence region comprising a pattern of a first power supply circuit and second power supply circuit, provided on a power supply substrate directly, arranged in accordance with the geometrical pattern of a first electrode and second electrode of a LED die, for achieving the object of increasing the package density.
It I still another object of the present invention to provide a light-emitting device having an enlarged area of active luminescence region comprising wire-bonding pads seated on a power supply substrate without performing a wire-bonding process on a LED die directly, the shade for the LED resulted from wire-bonding process may be avoided.
For the purpose of achieving aforementioned objects, the present invention provides a light-emitting device having an enlarged area of active luminescence region, the main structure thereof comprising at least one die light-emitting die, each including a die substrate provided with a second epitaxy layer defining at least one first surface and at least one second surface, the first surface being further formed with a first epitaxy layer thereon, an active luminescence region being naturally formed between the first epitaxy layer and the second epitaxy layer, a part of surface of the first epitaxy layer being provided with at least one first electrode, while a part of the surface of the second epitaxy layer being provided with at least one second electrode; and a power supply substrate provided with, on the surface thereof, at least one first power supply circuit and at least one second power supply circuit at positions corresponding to the first electrode and the second electrode, respectively, each first power supply circuit being electrically connected to another via a first connective circuit, while each second power supply circuit being connected to another via a second connective circuit, the first power supply circuit being electrically interconnected with the corresponding first electrode, while the second power supply circuit being electrically interconnected with the corresponding second electrode.
The structural features and the effects to be achieved may further be understood and appreciated by reference to the presently preferred embodiments together with the detailed description.
Referring to
A first electrode 331 is provided on the top surface of the first epitaxy layer 33, and two second electrodes 351 are disposed at both sides of the first electrodes 331, respectively, such that the second electrodes 351 may be contacted with the second surface 355 of the second epitaxy layer 35 and electrically insulated with the first epitaxy layer 33 and the first electrode 331 by means of an electrode insulation layer. The first electrode 331 and the second electrodes 351 are arranged alternately, in such a way that an uniform active current is allowed to flow through the active luminescence region 353, further resulting in enhancing luminous yield, and avoiding the damage for the active luminescence region 353 due to the local over-current density.
Furthermore, on the top surface of the power supply substrate 41, at least one first power supply circuit 431 and second power supply circuit 451 are provided directly at positions corresponding to the first electrode 331 and second electrode 351, on the LED die 30, respectively. Moreover, there are further provided with a first connective circuit 43 electrically connected to the first power supply circuit 431, and a second connective circuit 45 also electrically connected to each second power supply circuit 451. The number of the first power supply circuit 431 and second power supply circuit 451 is identical to that of the first electrode 331 and second electrode 351. The power supply substrate 41 may be formed from insulation material selected from the group consisting of Si3N4, Al2O3, AIN, BeO, as well as SiC, Si, GaN covered with dielectric material (SiO2, TiO2, Si3N4, and so on), as examples.
Subsequently, referring to
Furthermore, referring to
Additionally, an electrostatic discharge (ESD) protection device 57, such as Zener diode and Schottky diode, for example, may be further fixedly provided on the substrate 51, and electrically connected, at two electrodes thereof, to each of the first connective circuit 53 and the second power supply circuit 551, or to each of the second connective circuit 55 and the first power supply circuit 531 (not shown), respectively, so as to prevent apprehension for unexpected damage for the LED die 30 resulted from the effect of ESD. Thus, the normal operation for the LED die 30 may be ensured.
The most LED dies 30 may be provided on the substrate 51 with smallest area, since the plurality of first power supply circuits 531 and second power supply circuits 551 on the substrate 51 are established in correspondence with the number of the first electrodes 331 and second electrodes 351 of the LED dies 30. Thereby, the object of raising the package density, and thus light, thin, short, as well as small light-emitting device may be further obtained.
Furthermore, referring to
On a power supply substrate 71, there are provided with a first connective circuit 73, further connectedly provided with a plurality of first power supply circuits 731; and a second connective circuit 75, connected with a plurality of second power supply circuits 751, in which the locations and the number of the plurality of first circuits 731 and second circuits 751 are both in correspondence with those of the first electrodes 631 and second electrodes 651.
Further, a first bonding pad 731, provided on the first connective circuit 73 in place, and a second bonding pad 755, also provided on the second connective circuit 75 in place, are used for wire-bonding process. The direct damage for the LED die 60 resulted from wire-bonding process may be avoided, because the first bonding pad 735 and the second bonding pad 755 are provided on the power supply substrate 71, instead of being provided on the LED die 60 directly. Thereby, the normal operation for the LED die 60 may be protected.
Finally, referring to
The working current density in each active luminescence region 653 is extremely uniform, due to the symmetry resulted from the alternating establishment of the first electrodes 631 and second electrodes 651. Moreover, the second electrodes 651 are conducted with each other via the second connective circuit 75 on the power supply substrate 71. Therefore, differently from the conventional structure, apprehension for occupying the area of the active luminescence region (235) which, provided on the LED die (20), is required for connecting individual second electrodes (291), may be eliminated.
Furthermore, the present invention is described with the second electrode presented as linear arrangement in the above embodiments, but is not limited thereto. The annular arrangement, staggered arrangement, and other symmetrically geometrical arrangements are also used for the second electrode, only providing the first connective circuit 73 and the second connective circuit 75 onto the power supply substrate 71, instead of onto the LED die 60 directly, is required. Thus, the effect of enlarging the active luminescence area may be then achieved.
Furthermore, although the second electrodes 351, 651 of the LED dies 30, 60 are designed as being disposed in a horizontal level approximate to or the same as that in which the first electrodes 331, 631 are disposed, respectively, the conventional LED die (20) shown in
Furthermore, although the power supply substrates 41, 51, 71 are made from an insulation material in the aforementioned embodiments, other materials such as SiS, Si, and GaAs, as examples, may be substitutively used in different embodiments, only of insulation material further covering these power supply substrates is required.
To sum up, it should be understood that the present invention is related to a light-emitting device, particularly to a light-emitting device having an enlarged area of active luminescence region so as to enhance the brightness, allowed for a relatively enlarged area of active luminescence region, and thus an enhanced luminous yield.
The foregoing description is merely one embodiment of present invention and not considered as restrictive. All equivalent variations and modifications in process, method, feature, and spirit in accordance with the appended claims may be made without in any way from the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 093101497 | Jan 2004 | TW | national |
