In this study, the change of optical characteristics was studied according to the micro optical pattern provided by photo lithography followed by thermal reflow process. The shape and luminance variation with micro pattern was evaluated by SEM and spectrometers. Also, we analyzed the luminance characteristics using the 3D-optical simulation (Optis works) program. As a result, we found that the radius of curvature(R) in micro pattern is decreased up to 77%(150℃) compared to the radius of curvature at the condition 100℃, which is caused by efficient reflow of organic material without chemical changes. The highest enhancement of brightness with optimum micro pattern was obtained at the condition of 120℃ reflow process. The brightness gain with optical micro patterns is more than 15% at the condition of R=16.95 um, θ =77.14° compared to original optical source. The results of light simulation with various radius of curvature and side angle of pattern shows the similar result of experiment evaluation of light behavior on optical micro patterns. It is regarded that the more effect on light enhancement was contributed by side angle which is effective factor on light reflection, rather than the curvature of micro-patterns.
Abstract: This study investigated the characteristics of fracture behavior and mode on solder joints before and after thermal shock test for automotive application component using Sn-3.0Ag-0.5Cu solder, which has a outstanding property as lead-free solder. The shear strength was decreased with thermal cycle number, after 432 cycles of thermal shock test. In addition, fracture mode was verified to ductile, brittle fracture and base materials fracture such as different kind fractured mode using SEM and EDS. Before the thermal shock, the fractured mode was found to typical ductile fracture in solder layer. After thermal shock test, especially, Ag was found on fractured portion as roughest surface. Moreover, it occurred delamination between a PCB and a Cu land. Before thermal shock test, most of fractured mode in solder layer has dimples by ductile fracture. However, after thermal shock test, the fractured mode became a combination of ductile and brittle fracture, and it also could find that the fracture behavior varied including delamination between substrate and Cu land.
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Reliability Evaluation of Epoxy Solder Joints for Medical Electronic Devices Yu-Jae Jeon, Min-Soo Kang Journal of the Korean Society of Manufacturing Technology Engineers.2021; 30(2): 127. CrossRef
Solder Bump Deposition Using a Laser Beam Won-Suk Choi, Jea-Woon Kim, Jong-Hyeong Kim, Joo-Han Kim Transactions of the Korean Society of Mechanical Engineers A.2012; 36(1): 37. CrossRef
Laser-assisted deposition of Cu bumps for microelectronic packaging Won-Seok CHOI, Joohan KIM Transactions of Nonferrous Metals Society of China.2012; 22: s683. CrossRef
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