In this paper, we improved the light extraction efficiency by considering an additional upper layer on the top surface of a conventional LED. We simulated the LED's light emission as functions of the thickness and the refractive index of the upper layer, and analyzed how the condition improved the light efficiency. When the refractive index's range was from 1.05 to 1.40, the LED emission increased. For that case, the emission also increased as the thickness increased. We experimentally showed that the light extraction efficiency was improved about 22% by forming the upper layer on the top surface of an LED using material with refractive index 1.30 at 589.3 nm. It is expected that forming the upper layer on an LED can easily improve the extraction efficiency.

We present the thermal analysis result of die bonding for a high power LED package using a metal hybrid silicone adhesive structure. The simulation structure consists of an LED chip, silicone die adhesive, package substrate, silicone-phosphor encapsulation, Al PCB and a heat-sink. As a result, we demonstrate that the heat generated from the chip is easily dissipated through the metal structure. The thermal resistance of the metal hybrid structure was 1.662 K/W. And the thermal resistance of the total package was 5.91 K/W. This result is comparable to the thermal resistance of a eutectic bonded LED package.

Optimum Designs of 2 Segment LED Reflectors for Various Light Output Distributions on the Surface of an LED Chip (Received September 21, 2012; Revised manuscript December 4, 2012; Accepted December 7, 2012) It is important to control the beam pattern of an LED by the design of a reflector. The optimum conditions of the structure parameters for the 2 segment LED reflector are analyzed and compared as they vary depending on the various intensity distributions of light output on the LED chip surface. It is also interesting that combining various types of reflectors is possible to give several efficient beam patterns, such as the maximum intensity profile or relatively wide controllability of beam angle.

In this paper, we design a helical fin structure for the heat sink for a high-power LED lighting module, and analyze its thermal properties. By means of the helical fin structure, we can obtain about 14% larger surface area for the limited volume and it can decrease the LED chip temperature by about 12%. Because this helical fin heat sink has 15% less total volume than a conventional one, we can also expect to reduce the production cost due to these structural properties.

In this paper, in order to enhance the image reconstruction performance of white light scanning interferometry(WLI), we demonstrate the scattered point noise filtering performance of post-processing methods. Median filtering is similar to using an averaging filter. Because the median value is less sensitive than the mean to extreme values, the median filter can remove the scattered point noise from a height-map without significantly reducing the sharpness of the image. In several specific cases, however, the median filter can't remove the scattered point noise. Therefore, we propose a comparative mean filter that uses order-statistic filtering and the mean of the neighborhood pixels. The performance is demonstrated by measuring an array of metal solder balls fabricated on PCB. The proposed method reduced the noise pixels by 4.4 percent.