Reliability of high-power LED packaging and assembly
In recent years, it has been demonstrated that the lighting efficacy of today’s LEDs (Light Emitting Diodes), in particular the GaN-based, has exceeded the efficacy of traditional light sources, such as, white incandescent and halogen light bulbs. Consequently, the use of high-brightness LEDs operated under high power condition as a light source has attracted serious attention. While GaNbased LEDs are operated under high power condition (over 1 W at least), significant heat generated at the active region (MultiQuantum Wells) would cause high junction temperature and LED chip temperature. As a result, the efficiencies of GaN-based LEDs would deteriorate, such as, internal quantum efficiency, the conversion efficiency of the phosphor, and light extraction efficiency of epoxy lens. In addition, the thermal degradation on the various components of LED chips would be another major reliability issue for the high power LED. Hence, more stringent reliability performance of high-power LED packaging design and materials are highly in demand; extracting the light from the high-power LED chips at a consistent and reliable color for a long time. Thus, this special issue ‘‘Reliability of high-power LED packaging and assembly’’ focuses on three key aspects of high-power LEDs packaging; (1) reliability failure mode analysis, (2) thermal analysis and management, (3) optical design and light emitting efficiency degradation. Also, it is an aim to further provide the essential technical insights, the knowledge, and expertise of the technology to get to the top of this competitive industry. This special issue comprises 25 contribution papers. In the first paper of this special issue, Prof. M.G. Pecht gives the overall review on the Reliability of LEDs’ package. Then, followed by six specific topics on the high-power LEDs’ reliability; Dr. Sima Tarashioon reports the approach to ‘‘Design for Reliability’’ in solid state lighting system at high temperature. Prof. K.N. Chiang and Prof. Matteo Meneghini discuss the LED chip and package-related degradation on high-power light-emitting Diodes. Prof. Wood-Hi Cheng evaluates the failure of the encapsulation materials in accelerated thermal tests. Prof. Ray-Hua Horng reports the failure modes of LED Packages. Prof. M.Y. Tsai studies the strength of high-power LED die-attachment using Point-Load and Line-Load tests. In the second group of this special issue, there are seven papers studying the thermal management on the high-power LEDs. Prof. Moo Whan Shin, Prof. Samuel Graham, and Prof. M.Y. Tsai investigate the thermal performance and measurements of LED lighting module. C.Y. Liu and Prof. Chih-Ming Chen study the thermal management and measurement of first-level LED chip package. Dr. Han Kuei Fu reports the thermal silicon and AlN submounts for flip-chip light-emitting diodes. Prof. Ching Cherng Sun discusses the large area die bonding materials and their corresponding mechanical and thermal properties. Vertical LED structure is a promising high-power LED for general lighting. Prof. Shang-Ping Ying studies the package for the vertical high-power LED structure. At last,