Light emitting device
A light emitting device is proposed, which emits light while connected to the power. The light emitting device includes a light emitting element having at least two electrodes disposed at the side of the light output surface thereof; and a base member having a recess and lead portions corresponding to the electrodes, the light emitting element being mounted on the base member and received in the recess, wherein the light output surface faces toward opening of the recess that becomes smaller while approaching the light output surface, and the electrodes are respectively in electrical connection with the lead portions that extend from the connection positions to outer edge of the base member for power connection. The light emitting device of the present invention has advantages of short current path, low series thermal resistance and low cost. In addition, the depth of the recess can further be increased to improve light collecting efficiency.
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1. Field of the Invention
The present invention relates to light emitting devices and, more particularly, to a light emitting device that can be applied to high power light emitting diodes.
2. Description of Related Art
Currently, light emitting diodes (LEDs) that are characterized by long lifetime, small volume, low heat dissipation, low power consumption, fast response speed and single color light emission are widely used in indicator lights, bill boards, traffic lights, auto lamps, display panels, communication tools, consumer electronics and so on. Accordingly, different packaging techniques are developed for LEDs packaging, which results in different package structures of LEDs.
FIGS. 1(A) to 1(C) show a flip chip packaging process. As shown in
FIGS. 2(A) to 2(C) show a wire bonding packaging process. As shown in
In the above two packaging processes, because the molding compound and the substrate have different expansion factors, deformation and stripping are easy to happen. In addition, since the LED chip is electrically connected to the outside through the aluminum or ceramic substrate, the conductive path is very long, which results in too much heat absorption by the aluminum or ceramic substrate, thereby making the mass production difficult. Furthermore, if several chip products are applied to the aluminum or ceramic substrate, the aluminum or ceramic substrate becomes so weak that it needs to be processed before the reflow process, thereby resulting in high fabrication cost.
FIGS. 3(A) to 3(C) and FIGS. 4(A) to 4(C) show two packaging processes which respectively use lead frames 30 and 40 and heat sinks 31 and 41. As shown in FIGS. 3(A) and 4(A), the heat sinks 31 and 41 located on the lead frames 30 and 40 are respectively coated with silver paste 32 and 42. As shown in FIGS. 3(B) and 4(B), flip chip LED chip devices 33 and 43 are respectively attached to the lead frames 30 and 40. Afterwards, a wire bonding process is performed. Subsequently, the underfill and package processes are performed and final package structures are shown in FIGS. 3(C) and 4(C).
In the above two packaging processes, high series thermal resistance leads to low reliability. Further, since the stack technique is used in the above two packaging processes, the packaged products become very thick. To facilitate processes that are performed from the front side of the package structure, the depth of the recess must be shallow (as shown in FIGS. 4(A) to 4(C)). However, such a shallow recess will affect light collecting efficiency.
FIGS. 5(A) to 5(C) and FIGS. 6(A) to 6(C) show two packaging processes which use ceramic substrates and injection molded lead frames. It should be noted that an aluminum substrate must be further attached to the ceramic substrate. Thus, high cost of the ceramic substrate and addition of the aluminum substrate result in high fabrication cost. In addition, as shown in FIGS. 6(A) to 6(C), injection molding technique results in high series thermal resistance of light emitting device. Accordingly, the light emitting device can not be used in high power LED package. As described above in FIGS. 4(A) to 4(C), there also exists the problem of bad light collecting efficiency.
Accordingly, there is a need to develop a low thickness LED package structure which has low series thermal resistance and low packaging and application cost and can improve light collecting efficiency.
SUMMARY OF THE INVENTIONAccording to the above defects, a primary objective of the present invention is to provide a thin thickness light emitting device.
Another objective of the present invention is to provide a light emitting device which can reduce the series thermal resistance.
A further objective of the present invention is to provide a light emitting device which can reduce the fabrication cost.
Still another objective of the present invention is to provide a light emitting device which can improve the light collecting efficiency.
To achieve the above and other objectives, the present invention discloses a light emitting device, at least comprising: a light emitting element with at least two electrodes disposed at the side of the light output surface thereof; and a base member having a recess and lead portions corresponding to the electrodes, the light emitting element being mounted on the base member and received in the recess, wherein the light output surface faces toward opening of the recess that becomes smaller while approaching the light output surface, and the electrodes are respectively in electrical connection with the lead portions that extend from the connection positions to outer edge of the base member for power connection.
Compared with the prior art, the light emitting device of the present invention achieves a much simpler light emitting device of thin thickness by combining a light emitting element with a base member which is connected to the power through lead portions of the base member, thereby resulting in short current path and low series thermal resistance and low cost. In addition, the depth of the recess can be increased to improve the light collecting efficiency.
BRIEF DESCRIPTION OF DRAWINGSFIGS. 1(A) to 1(C) are diagrams illustrating a first light emitting diode package structure according to the prior art;
FIGS. 2(A) to 2(C) are diagrams illustrating a second light emitting diode package structure according to the prior art;
FIGS. 3(A) to 3(C) are diagrams illustrating a third light emitting diode package structure according to the prior art;
FIGS. 4(A) to 4(C) are diagrams illustrating a fourth light emitting diode package structure according to the prior art;
FIGS. 5(A) to 5(C) are diagrams illustrating a fifth light emitting diode package structure according to the prior art;
FIGS. 6(A) to 6(C) are diagrams illustrating a sixth light emitting diode package structure according to the prior art;
FIGS. 7(A) to 7(E) are diagrams illustrating detailed structure of a light emitting device according to the present invention;
FIGS. 8(A) to 8(B) are diagrams illustrating structures of a light emitting device according to two other embodiments of the present invention;
FIGS. 9(A) to 9(B) are diagrams respectively illustrating structure of a base member having a deeper recess and structure of a light emitting device comprising such a base member according to the present invention;
Hereunder, embodiments of the present invention will be described in full detail with reference to the accompanying drawings.
FIGS. 7(A) to 7(E) are diagrams showing detailed structure of a light emitting device according to the present invention. The light emitting device of the present invention at least includes a light emitting element 60 (shown in
As shown in
As shown in
As shown in
As shown in
As shown in
To solve the heat dissipating problem of the light emitting device, the present invention proposes another embodiment, as shown in
Therefore, the light emitting device of the present invention at least includes a light emitting element having at least two electrodes located at the side of the light output surface thereof and a base member to which the light emitting element can be mounted. Therein, the light emitting element is received in a recess of the base member with its light output surface facing toward the opening of the recess that gradually decreases while approaching the light output surface and the electrodes of the light emitting elements are electrically connected with lead portions of the base member that extend toward the outer edge of the base member for power connection. As a result, the present invention achieves a light emitting device of thin thickness, which accordingly has advantages of short current path, low series thermal resistance and low cost. In addition, the depth of the recess can be increased to improve light collecting efficiency, which is not limited to the depth of 6 mm as in the prior art. Further, compared with the prior art that only can mount the light emitting element from the front side of the base member, since a hollow base member is used in the present invention, the light emitting element can be mounted into the recess from the back side of the base member, thereby facilitating the mounting process.
The invention has been described using exemplary preferred embodiments. However, it is to be understood that the scope of the invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements. The scope of the claims, therefore, should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.
Claims
1. A light emitting device, at least comprising:
- a light emitting element having at least two electrodes disposed at a side of a light output surface thereof;
- a base member comprising a recess and a plurality of lead portions corresponding to the electrodes, the light emitting element being mounted on the base member and received in the recess, wherein the light output surface faces toward an opening of the recess that converges while approaching the light output surface, and the electrodes are respectively in electrical connection with the lead portions that extend from the connection positions to outer edge of the base member for power connection.
2. The light emitting device of claim 1, wherein the light emitting element comprises at least one substrate provided with electrodes for power connection and at least one light emitting chip mounted on the substrate and electrically connected with the substrate.
3. The light emitting device of claim 1 or 2, wherein the light emitting element is selected from the group consisting of single color single chip, single color multi-chip, multi-color multi-chip and chip(s) emitting ultraviolet light.
4. The light emitting device of claim 2, wherein the light emitting chip in a flip-chip configuration is electrically connected with the substrate via one of the group consisting of gold balls, tin balls and electrically and thermally conductive material.
5. The light emitting device of claim 2, wherein the light emitting chip is an LED chip.
6. The light emitting device of claim 2, wherein the substrate is selected from the group consisting of Si, Al and C.
7. The light emitting device of claim 1, wherein the base member is a lead frame.
8. The light emitting device of claim 7, wherein the lead frame is formed by one of the methods consisting of injection molding and assembly.
9. The light emitting device of claim 7, wherein the lead frame is mainly formed of one of the group consisting of PPA resin, PC thermoplastic material and insulating material.
10. The light emitting device of claim 1, wherein a light reflecting portion is further disposed in the recess adjacent to the light output surface such that the light emitted from the light emitting element can be reflected to walls of the recess to form a substantially collimated light beam so as to improve light efficiency.
11. The light emitting device of claim 10, wherein the light reflecting portion is formed of reflective material by one of the methods consisting of electroplating and assembling.
12. The light emitting device of claim 1, wherein a light converting portion is further disposed in the recess adjacent to the light output surface to change the wavelength of the light emitted from the light emitting element so as to improve light efficiency.
13. The light emitting device of claim 12, wherein the light converting portion is formed of fluorescent converting material by coating.
14. The light emitting device of claim 10, wherein the recess is filled with sealing member to fix the light reflecting portion and the light emitting element to the base member.
15. The light emitting device of claim 12, wherein the recess is filled with sealing member to fix the light converting portion and the light emitting element to the base member.
16. The light emitting device of claim 15, wherein the sealing member further forms a lens shape at the light output surface of the light emitting element to improve light collecting efficiency.
17. The light emitting device of claim 1, wherein the lead portions are formed of electrically conductive conductor.
18. The light emitting device of claim 17, wherein the conductor is one of the group consisting of Au, Ag, Cu, Sn, Al and conductive material.
19. The light emitting device of claim 1 or 17, wherein the lead portions are electrically connected with the electrodes of the light emitting element through one of the group consisting of conductive adhesive, gold balls, tin balls and conductive bonding material.
20. The light emitting device of claim 19, wherein the conductive adhesive is one of the group consisting of silver paste, solder paste and solder paste containing lead.
21. The light emitting device of claim 1 further includes a thermal conductor attached to a surface of the light emitting element opposite to the light output surface for heat dissipation.
22. The light emitting device of claim 21, wherein the thermal conductor is formed of one of the group consisting of Al, Cu, Fe and material having a thermal conductivity of at least 50 W/mK.
23. The light emitting device of claim 21, wherein an adhesive layer is further disposed between the thermal conductor and the light emitting element.
24. The light emitting device of claim 23, wherein the adhesive layer is formed of heat sink paste.
25. A light emitting device, comprising:
- a light emitting element having at least two electrodes disposed at the side of the light output surface thereof;
- a base member having a recess and lead portions corresponding to the electrodes, the light emitting element being mounted on the base member and received in the recess, wherein the light output surface faces toward opening of the recess that becomes smaller while approaching the light output surface, and the electrodes are respectively in electrical connection with the lead portions that extend from the connection positions to outer edge of the base member for power connection, and a light reflecting portion is disposed in the recess adjacent to the light output surface such that the light emitted from the light emitting element can be reflected to walls of the recess to form a substantially collimated light beam so as to improve light efficiency, the recess being filled with sealing member to fix the light reflecting portion and the light emitting element to the base member; and
- a thermal conductor attached to a surface of the light emitting element opposite to the light output surface for heat dissipation.
26. The light emitting device of claim 25, wherein the light emitting element comprises at least one substrate provided with electrodes for power connection and at least one light emitting chip mounted on the substrate and electrically connected with the substrate.
27. The light emitting device of claim 25 or 26, wherein the light emitting element comprises one of the group consisting of single color single chip, single color multi-chip, multi-color multi-chip and chip(s) emitting ultraviolet light.
28. The light emitting device of claim 26, wherein the light emitting chip in a flip-chip configuration is electrically connected with the substrate via one of the group consisting of gold balls, tin balls and electrically and thermally conductive material.
29. The light emitting device of claim 26 or 8, wherein the light emitting chip is an LED chip.
30. The light emitting device of claim 26, wherein the substrate is made of one of the group consisting of Si, Al and C.
31. The light emitting device of claim 25, wherein the base member is a lead frame.
32. The light emitting device of claim 31, wherein the lead frame is formed by one of the methods consisting of injection molding and assembly.
33. The light emitting device of claim 31 or 32, wherein the lead frame is mainly formed of one of the group consisting of PPA resin, PC thermoplastic material and insulating material.
34. The light emitting device of claim 25, wherein the lead portions are formed of electrically conductive conductor.
35. The light emitting device of claim 34, wherein the conductor is one of the group consisting of Au, Ag, Cu, Sn, Al and conductive material.
36. The light emitting device of claim 25 or 34, wherein the lead portions are further electrically connected with the electrodes of the light emitting element through one of the group consisting of conductive adhesive, gold balls, tin balls and conductive bonding material.
37. The light emitting device of claim 36, wherein the conductive adhesive is one of the group consisting of silver paste, solder paste and solder paste containing lead.
38. The light emitting device of claim 25, wherein the sealing member forms a lens shape at the light output surface of the light emitting element to improve light collecting efficiency.
39. The light emitting device of claim 25, wherein light reflecting portion is formed of reflective material by one of the methods consisting of electroplating and assembling.
40. The light emitting device of claim 25, wherein the thermal conductor is formed of one of the group consisting of Al, Cu, Fe and material having a thermal conductivity of at least 50 W/mK.
41. The light emitting device of claim 25, wherein an adhesive layer is further disposed between the thermal conductor and the light emitting element.
42. The light emitting device of claim 41, wherein the adhesive layer is formed of heat sink paste.
43. A light emitting device, comprising:
- a light emitting element with at least two electrodes disposed at the side of the light output surface thereof;
- a base member having a recess and lead portions corresponding to the electrodes, the light emitting element being mounted on the base member and received in the recess, wherein the light output surface faces toward opening of the recess that becomes smaller while approaching the light output surface, and the electrodes are respectively in electrical connection with the lead portions that extend from the connection positions to outer edge of the base member for power connection, and a light converting portion is disposed in the recess adjacent to the light output surface to change the wavelength of the light emitted from the light emitting element so as to improve light efficiency, the recess being filled with sealing member to fix the light converting portion and the light emitting element to the base member; and
- a thermal conductor attached to a surface of the light emitting element opposite to the light output surface for heat dissipation.
44. The light emitting device of claim 43, wherein the light emitting element comprises at least one substrate provided with electrodes for power connection and at least one light emitting chip mounted on the substrate and electrically connected with the substrate.
45. The light emitting device of claim 43, wherein the light emitting element comprises one of the group consisting of single color single chip, single color multi-chip, multi-color multi-chip and chip(s) emitting ultraviolet light.
46. The light emitting device of claim 44, wherein the light emitting chip in a flip-chip configuration is electrically connected with the substrate via one of the group consisting of gold balls, tin balls and electrically and thermally conductive material.
47. The light emitting device of claim 44, wherein the light emitting chip is an LED chip.
48. The light emitting device of claim 44, wherein the substrate is made of one of the group consisting of Si, Al and C.
49. The light emitting device of claim 43, wherein the substrate is a lead frame.
50. The light emitting device of claim 49, wherein the lead frame is formed by one of the methods consisting of injection molding and assembly.
51. The light emitting device of claim 49, wherein the lead frame is mainly formed of one of the group consisting of PPA resin, PC thermoplastic material and insulating material.
52. The light emitting device of claim 43, wherein the lead portions are formed of electrically conductive conductor.
53. The light emitting device of claim 52, wherein the conductor is one of the group consisting of Au, Ag, Cu, Sn, Al and conductive material.
54. The light emitting device of claim 43 or 52, wherein the lead portions are electrically connected with the electrodes of the light emitting element through one of the group consisting of conductive adhesive, gold balls, tin balls and conductive bonding material.
55. The light emitting device of claim 54, wherein the conductive adhesive is one of the group consisting of silver paste, solder paste and solder paste containing lead.
56. The light emitting device of claim 43, wherein the sealing member further forms a lens shape at the light output surface of the light emitting element to improve light collecting efficiency.
57. The light emitting device of claim 43, wherein the light converting portion is formed of fluorescent converting material by coating.
58. The light emitting device of claim 43, wherein the thermal conductor is formed of one of the group consisting of Al, Cu, Fe and material having a thermal conductivity of at least 50 W/mK.
59. The light emitting device of claim 43, wherein an adhesive layer is further disposed between the thermal conductor and the light emitting element.
60. The light emitting device of claim 59, wherein the adhesive layer is formed of heat sink paste.
Type: Application
Filed: May 8, 2006
Publication Date: Mar 29, 2007
Applicant:
Inventors: Ming-Te Lin (Hsinchu Hsien), Ming-Yao Lin (Hsinchu Hsien), Chia-Chang Kuo (Hsinchu Hsien), Sheng-Pan Huang (Hsinchu Hsien), Wen-Yung Yeh (Hsinchu Hsien)
Application Number: 11/429,235
International Classification: H01L 33/00 (20060101);