This application claims priority of Taiwanese Application No. 096105079, filed on Feb. 12, 2007.
1. Field of the Invention
This invention relates to a method for making a light emitting device, more particularly to a method involving isolating vertical-feedthrough-LED chips on a chip-mounting board using a patterned photoresist for making a light emitting device.
2. Description of the Related Art
U.S. Pat. No. 7,128,438 discloses a light display structure that includes strip-like first and second conductors, a plurality of LED chips disposed between and in electrical contact with the first and second conductors, and spacers disposed between the first and second conductors and defining apertures, each of which receives a respective one of the LED chips. The spacers are formed from a strip of a molded polymer.
The aforesaid conventional light display structure is disadvantageous in that the manufacturing process thereof is relatively complicated.
Therefore, the object of the present invention is to provide a method for making a light emitting device that can overcome the aforesaid drawback associated with the prior art.
According to this invention, there is provided a method for making a light emitting device. The method comprises: (a) preparing a chip-mounting board having a conductive surface; (b) mounting a plurality of vertical-feedthrough-LED chips on the conductive surface of the chip-mounting board such that a first electrode of each of the vertical-feedthrough-LED chips is in electrical contact with the conductive surface; (c) forming a photoresist layer that cooperates with the chip-mounting board to enclose the vertical-feedthrough-LED chips; (d) patterning the photoresist layer by photolithography techniques to form a plurality of holes in the photoresist layer in such a manner that each of the holes exposes at least a portion of a second electrode of a respective one of the vertical-feedthrough-LED chips; and (e) forming a conductive layer that covers the patterned photoresist layer and the exposed portions of the second electrodes of the vertical-feedthrough-LED chips, which are exposed from the holes in the photoresist layer.
Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment of this invention, with reference to the accompanying drawings, in which:
In this preferred embodiment, the chip-mounting board 21 is composed of a supporting substrate 210 and a conductive film 212 formed on the supporting substrate 210 and defining the conductive surface 221 of the chip-mounting board 21.
The method further includes a step of forming a plurality of parallel strip-like cleaving grooves 211 in the chip-mounting board 21 after step (a) and prior to step (b) (see
The method further includes a step of breaking an assembly of the conductive layer 5, the photoresist layer 4, the vertical-feedthrough-LED chips 3, and the chip-mounting board 21 along the strip-like cleaving grooves 211 after step (e) so as to form a plurality of light bars (see
The method can optionally further include a step of roughening a back surface 213 of the chip-mounting board 21 (see
In this embodiment, the chip-mounting board 21 and the first electrode 31 of each of the vertical-feedthrough-LED chips 3 are transparent, the photoresist layer 4 is made from a negative photoresist material, and the second electrode 32 of each of the vertical-feedthrough-LED chips 3 is reflective so that a back-side exposure can be conducted in step (d) in such a manner that a portion of the photoresist layer 4, which fills the strip-like cleaving grooves 211 and the gaps 42 among the vertical-feedthrough-LED chips 3, is exposed to a radiation through the back surface 213 of the chip-mounting board 21, and that the remainder of the photoresist layer 4, which is covered by the second electrodes 32 of the vertical-feedthrough-LED chips 3, remains unexposed and is removed subsequently to form the holes 41. Alternatively, the photoresist layer 4 can be made from a positive photoresist material. As such, a front-side exposure is conducted using a mask to expose the portion of the photoresist layer 4 to a radiation.
The supporting substrate 210 of the chip-mounting board 21 is preferably made from a rigid material selected from the group consisting of glass, quartz, a diffuser plate, a thick plastic plate, and the like. Each of the strip-like cleaving grooves 211 formed in the chip-mounting board 21 is preferably defined by a V-shaped groove-defining wall. Preferably, the ratio of the depth of each of the strip-like cleaving grooves 211 to the layer thickness of the chip-mounting board 21 ranges from 1:4 to 4:5 so as to facilitate the breaking of the chip-mounting board 21.
As illustrated in
Referring to
To achieve a white light, the vertical-feedthrough-LED chips 3 of each of the light bars thus formed can be composed of red-light-emitting diodes, green-light-emitting diodes, and blue-light-emitting diodes. Alternatively, the back surface 213 of the chip-mounting board 21 can be coated with a phosphor material to convert the wavelength of the light from the vertical-feedthrough-LED chips 3 so as to achieve the white light.
It is noted that the supporting substrate 210 of the chip-mounting board 21 can also be made from a conductive material, such as a metallic plate. As such, formation of the conductive film 212 can be dispensed with. When a stainless steel plate is used as the chip-mounting board 21, formation of the strip-like cleaving grooves 211 can be conducted using wire cutting techniques.
The merits of the method of this invention will become apparent with reference to the following Example.
In this example, an indium tin oxide (ITO) film was deposited on a glass substrate having a layer thickness of about 700 μm so as to form the chip-mounting board 21 which was subsequently cut to form a plurality of the strip-like cleaving grooves 211, each of which has a depth of about 350 μm. A plurality of the vertical-feedthrough-LED chips 3 were then mounted on the chip-mounting board 21. The assembly was then subjected to a coating operation using a spinning coater for forming the photoresist layer 4 on the assembly, which was subsequently subjected to an exposing operation using a back-side exposure system. The exposed portion of the photoresist layer 4 was hardened, while the unexposed portion of the photoresist layer 4, which was disposed on the vertical-feedthrough-LED chips 3, was then removed to form the holes 41 in the photoresist layer 4. A conductive layer 5 was then formed on the vertical-feedthrough-LED chips 3 and the remainder portion of the photoresist layer 4. The assembly thus formed was then subjected to a breaker to break the same along the strip-like cleaving grooves 211 so as to form the light bars.
By virtue of the processes of forming the photoresist layer 4 and the conductive layer 5, the method for making the light emitting device of this invention is simpler than the aforesaid conventional method. In addition, the size of the light emitting device formed by the method of this invention can be reduced as compared to the aforesaid conventional light emitting device.
While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation and equivalent arrangements.
Number | Date | Country | Kind |
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096105079 | Feb 2007 | TW | national |