News Column

Researchers Submit Patent Application, "Light Emitting Device and Manufacture Method Thereof", for Approval

July 23, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors TU, Chuan-Cheng (Tainan City, TW); WU, Jen-Chau (Hsinchu City, TW); SHIEH, Yuh-Ren (Hsinchu County, TW); CHEN, Tzer-Perng (Hsinchu City, TW); HSIEH, Min-Hsun (Hsinchu City, TW), filed on November 18, 2013, was made available online on July 10, 2014.

The patent's assignee is Epistar Corporation.

News editors obtained the following quote from the background information supplied by the inventors: "For conventional light emitting device (LED) packages, a LED chip is mounted onto the sub-mount using the epoxy put thereon to form a LED element, and the process is called 'Die Bonding'. Typically, the epoxy used in 'Die Bonding' can be silver filled epoxy or other non-conductive resin. Then, the LED elements are assembled onto the circuit board. For a flip-chip LED, the p-type conductive layer and the n-type conductive layer are exposed on the same side to have the positive electrode and the negative electrode on the same side of the LED structure. And the LED structure with the positive electrode and the negative electrode is flipped and disposed on the solder without wire bonding. However, conventional flip-chip LEDs still require 'Dicing' and 'Die Bonding' for connecting and mounting the circuit board. If the electrodes of flip-chip LEDs have large contact area to be directly connected to the circuit board, a number of conventional packaging processes for LEDs can be skipped.

"The operating current of a conventional LED is typically several tens to several hundreds of mAs. Therefore, the brightness of a conventional LED is not suitable for illumination purpose. When lots of LEDs are assembled into a LED lamp to improve the brightness, the volume of the LED lamp increases accordingly and results in the loss of its market competitiveness. Therefore, to improve the brightness of a single LED is a necessary approach. However, as the LED advances towards high brightness, the operating current and power of a single LED become several times to several hundred times than those that a conventional LED requires. For example, the operating current of a high brightness LED is about several hundreds of mAs to several Amps (A). As a result, the heat generated by the LED becomes an important issue. 'Heat' seriously affects the performance of LEDs; for example, the thermal effect influences the wavelength of lights emitted from the LED, reduces the brightness of lights generated from the semiconductor device, and damages the LED device. Therefore, how to dissipate heat generated by the high power LED become the important issue of the LEDs.

"US Applications Nos. 2004/0188696 and 2004/0203189 disclosed a LED package and the method for manufacturing the same based on the Surface Mount Technology (SMT). Each LED package includes a LED chip, and each chip is flip-chip bonded onto a frontside of the sub-mount wafer using boning bump. A plurality of arrays of openings is drilled into the electrically insulating sub-mount wafer. A metal is applied to the drilled openings to produce a plurality of via arrays. The p-type and n-type contacts of each flip-chip bonded LED electrically communicate with a solderable backside of the sub-mount wafer through a via array. A thermal conduction path is provided for thermally conducting heat from the flip-chip bonded LED chip to the solderable backside of the sub-mount wafer. Subsequent to the flip-chip bonding, the sub-mount wafer is separated to produce the surface mount LED packages.

"However in US Applications Nos. 2004/0188696 and 2004/0203189, it requires drilled via array with filled metal within the sub-mount wafer and thus increases the manufacturing cost. Furthermore, it becomes complicated to flip-chip bond each chip onto the sub-mount wafer using bonding bump. Therefore, it would be beneficial if the LED packages have excellent thermal conductive paths without the provision of the sub-mount wafers."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "The present disclosure provides a method for forming a light-emitting apparatus. The method comprises the steps of providing a first board having a plurality of first metal contacts, providing a substrate, forming a plurality of light-emitting stacks and trenches on the substrate wherein the light-emitting stacks are apart from each other by the plurality of the trenches, bonding the light-emitting stacks to the first board, forming an encapsulating material commonly on the plurality of the light-emitting stacks, and cutting the first board and the encapsulating material to form a plurality of chip-scale LED units.

"In one embodiment of the present disclosure, the method further comprises forming an opaque layer in the trench and enclosing the light-emitting stacks for preventing the light emitted from neighboring light-emitting stacks from mutually interfering or crosstalk.

"In one embodiment of the present disclosure, the method further comprises selectively forming a first wavelength converting material on a first light-emitting stack and configured to convert the light emitted from the first light-emitting stack to a first light, selectively forming a second wavelength converting material on a second light-emitting stack and configured to convert the light emitted from the second light-emitting stack to a second light, and providing a third light-emitting stack devoid of any wavelength converting material formed thereon, wherein the light emitted from the first, second, and third light-emitting stacks is a blue light, and wherein the first light is a green light, and the second light is a red light.

"In one embodiment of the present disclosure, the method further comprises removing the substrate to expose a surface of the light-emitting stacks after bonding the light-emitting stacks to the first board and roughening the exposed surface of the light-emitting stacks.

"In one embodiment of the present disclosure, the method further comprises forming an underfill material substantially over the surface of the first board before bonding the light-emitting stacks to the first metal contacts.

"In one embodiment of the present disclosure, the method further comprises providing a second board having a plurality of second metal contacts, and bonding the plurality of chip-scale LED units to the second metal contacts of the second board.

BRIEF DESCRIPTION OF THE DRAWINGS

"The foregoing aspects and many of the attendant advantages of this disclosure will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

"FIGS. 1A-1E illustrate cross-sectional views of forming a light emitting device (LED) in accordance with one embodiment of the present disclosure;

"FIG. 1F illustrates LEDs in accordance with an embodiment of the present disclosure;

"FIGS. 2A-2D illustrate cross-sectional views of forming a LED array in accordance with one embodiment of the present disclosure;

"FIG. 2E illustrates the LED array connected to the circuit board in accordance with another embodiment of the present disclosure;

"FIG. 2F illustrates a LED array having a first conductive layer with a rough surface in accordance with one embodiment of the present disclosure;

"FIG. 2G illustrates a LED array package in accordance with an embodiment of the present disclosure;

"FIGS. 3A-3G illustrate one embodiment of a chip-scale RGB LED unit and the manufacturing method thereof in accordance the present disclosure;

"FIG. 4A is a top view of an LED array flip-bonded to a circuit board depicted in FIG. 3F;

"FIG. 4B is a top view of a chip-scale RGB LED unit depicting in FIG. 3G;

"FIG. 5A is a top view of an LED array flip-bonded to a circuit board depicted in accordance with another embodiment of the present disclosure;

"FIG. 5B is a top view of a chip-scale LED unit in accordance with one embodiment of the present disclosure;

"FIG. 5C is a cross-sectional view of a chip-scale LED unit in accordance with one embodiment of the present disclosure;

"FIG. 5D is a top view of a chip-scale LED unit in accordance with another embodiment of the present disclosure;

"FIG. 5E is a cross-sectional view of the chip-scale LED unit depicted in FIG. 5D;

"FIG. 6A illustrates a chip-scale RGB LED unit in accordance with another embodiment of the present disclosure;

"FIG. 6B illustrates a chip-scale LED unit in accordance with another embodiment of the present disclosure;

"FIG. 6C illustrates a chip-scale LED unit in accordance with another embodiment of the present disclosure;

"FIG. 7A illustrates a display module in accordance with one embodiment of the present disclosure;

"FIG. 7B illustrates a lighting module in accordance with one embodiment of the present disclosure; and

"FIG. 8 illustrates a lighting apparatus in accordance with one embodiment of the present disclosure."

For additional information on this patent application, see: TU, Chuan-Cheng; WU, Jen-Chau; SHIEH, Yuh-Ren; CHEN, Tzer-Perng; HSIEH, Min-Hsun. Light Emitting Device and Manufacture Method Thereof. Filed November 18, 2013 and posted July 10, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=2943&p=59&f=G&l=50&d=PG01&S1=20140703.PD.&OS=PD/20140703&RS=PD/20140703

Keywords for this news article include: Electronics, Circuit Board, Epistar Corporation.

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Source: Electronics Newsweekly


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