News Column

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

June 4, 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 CHEN, Tzer-Perng (Hsinchu City, TW); WU, Jen-Chau (Hsinchu City, TW); TU, Chuan-Cheng (Tainan City, TW); SHIEH, Yuh-Ren (Hsinchu County, TW), filed on January 16, 2014, was made available online on May 22, 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, which 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 are 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: "One aspect of the present invention is to provide a structure of a light emitting device which facilitates the light emitting efficiency of the LED.

"Another aspect of the present invention is to provide a LED in which the electrodes are effective thermal conductive paths.

"A further aspect of the present invention is to provide a LED in which the electrodes connect directly to the circuits of the circuit board.

"A further another aspect of the present invention is to provide a LED with a rough surface to improve the light extraction efficiency.

"A still further aspect of the present invention is to provide a LED array and a method for manufacturing the same. The LED array includes a plurality of LEDs on a substrate, and the electrodes of each LED connect directly to the circuits of the circuit board. After the plurality of LEDs are disposed on the circuit board, the substrate is removed and the surface of each LED can be further processed so as to improve the light extraction efficiency.

"In one embodiment, the present invention provides a method of forming a light emitting device (LED). The method includes: (a) forming a light emitting structure, the light emitting structure including a substrate, a first conductive layer on the substrate, an active layer on the first conductive layer, and a second conductive layer on the active layer, the active layer being a light emitting layer; (b) forming a first dielectric layer on the light emitting structure; forming a second dielectric layer on the first dielectric layer; (d) forming a first metal layer, the first metal layer being disposed on the light emitting structure and electrically-connected to the first conductive layer, a portion of the first metal layer being disposed on the first dielectric layer; (e) forming a second metal layer, the second metal layer being disposed on the light emitting structure and electrically-connected to the second conductive layer, a portion of the second metal layer being disposed on the first dielectric layer; (f) removing the substrate to expose a surface of the first conductive layer; and (g) roughening the surface of the first conductive layer to improve a light extraction efficiency. The first dielectric layer and the second dielectric layer electrically-isolate the first metal layer from the second metal layer. A portion of the first dielectric layer is a transparent layer, and a surface of the first dielectric layer contacting the first metal layer and/or the second metal layer is provided for reflecting the light emitted from the light emitting structure.

"In another embodiment, the present invention provides a light emitting device. The LED includes a light emitting structure, a first dielectric layer, a first metal layer, a second metal layer, and a second dielectric layer. The light emitting structure includes a first conductive layer, an active layer, and a second conductive layer. The active layer is disposed on the first conductive layer and is a light emitting layer. The second conductive layer is disposed on the active layer. The first dielectric layer is disposed on the light emitting structure. The first metal layer is disposed on the light emitting structure and is electrically-connected to the first conductive layer. A portion of the first metal layer is disposed on the first dielectric layer. The second metal layer is disposed on the light emitting structure and is electrically-connected to the second conductive layer. A portion of the second metal layer is disposed on the first dielectric layer. The second dielectric layer is disposed on the first dielectric layer. The first dielectric layer and the second dielectric layer electrically-isolate the first metal layer from the second metal layer. A portion of the first dielectric layer is a transparent layer, and a surface of the first dielectric layer contacting the first metal layer and/or the second metal layer is provided for reflecting the light emitted from the light emitting structure. The first conductive layer includes a rough surface so as to improve a light extraction efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

"The foregoing aspects and many of the attendant advantages of this invention 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 invention;

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

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

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

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

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

For additional information on this patent application, see: CHEN, Tzer-Perng; WU, Jen-Chau; TU, Chuan-Cheng; SHIEH, Yuh-Ren. Light Emitting Device and Manufacture Method Thereof. Filed January 16, 2014 and posted May 22, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=5544&p=111&f=G&l=50&d=PG01&S1=20140515.PD.&OS=PD/20140515&RS=PD/20140515

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

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


For more stories covering the world of technology, please see HispanicBusiness' Tech Channel



Source: Electronics Newsweekly


Story Tools






HispanicBusiness.com Facebook Linkedin Twitter RSS Feed Email Alerts & Newsletters