Thermal analysis of remote phosphor in LED modules

Phosphor plays an important role in LED packages by converting the wavelength of light and achieving specific color.The property and degradation of phosphor are strongly affected by the temperature.Some structural factors have been investigated in this paper and their effects are evaluated.Remote phosphor is an effective approach to improve the performance and reliability of LED modules and products.It is a trade-off that the final product design depends on both the thermal performance and the cost.     

Rheological and other physical characteristics of polysaccharides from two black yeast-like fungi

Two black yeast polysaccharides show similar non-Newtonian behavior when the effects of polysaccharide concentration, shear rate, pH, salt, and temperature on the viscosity of dispersions are examined. Both polysaccharides readily form viscous aqueous dispersions and can be cast into flexible films, and both stabilize oil–water emulsions. Each of these two polysaccharides occurs extracellularly in the culture fluids of two different black yeast-like fungi—Rhinocladiella elatior Mangenot (strain NRRL YB-4163) and Rhinocladiella mansonii (Castellani) Schol-Schwarz (strain NRRL Y-6272). This report appears to be the first on the rheology of an extracellular polysaccharide which contains the unusual sugar N-acetyl-D -glucosaminuronic acid.     

Formation and evolution of intermetallic layer structures at SAC305/Ag/Cu and SAC0705-Bi-Ni/Ag/Cu solder joint interfaces after reflow and aging

In this paper, the formation and evolution characteristics of the intermetallic compounds (IMCs) in SAC305/Ag/Cu and SAC0705-3.5Bi-0.05Ni/Ag/Cu solder during reflow and 150 °C isothermal aging are investigated. Experimental results indicate that Ag₃Sn forms as soon as the SAC305/Ag/Cu solder spheres wetted to the substrates. With increased soldering time, the Ag layer on a Cu substrate dissolved into the molten SAC305 solder and the interfacial IMC consisted of Cu₆Sn₅. The Ag layers show a faster dissolution rate in SAC0705-3.5Bi-0.05Ni/Ag/Cu than in SAC305/Ag/Cu, which is attributed to a larger concentration gradient of Ag for SAC0705-3.5Bi-0.05Ni/Ag/Cu. The formation and coarsening of a Cu₃Sn layer between Cu₆Sn₅ and the Cu substrate caused the formation of Kirkendall voids and delamination during aging in the SAC305/Ag/Cu. A small addition of Ni in the solder significantly suppressed the formation of a Cu₃Sn layer in the SAC0705-3.5Bi-0.05Ni/Ag/Cu, resulting in fewer voids in the soldering interface.     

The need for multi-scale approaches in Cu/low-k reliability issues

Since recent years, micro-electronic industry changed the basic materials from Al/SiO₂ to Cu/low-k in IC interconnect structure. As a consequence, new reliability issues at device/product level has been discovered, and most of the failure modes have the characteristics of multi-scale: the failure of the μm or nm induces the malfunction of the device/product. Under the pressure of the time-to-market, the industries, universities and research institutes developed numerous multi-scale simulation technologies/tools to analyze the failure mechanism and to achieve the high reliability design with the capability of high volume production and low cost. This paper reviews the multi-scale modeling techniques for reliability and processing issues in Cu/low-k IC back-end structure, from the continuum level to the atomic scale.     

Platform Alarming Through Multiple Agencies

The offshore oil and gas industry strives to make every process safe for operators and employees. Unfortunately, it is not inconceivable that dangerous life-threatening conditions present themselves. Should an undesirable condition occur, it is ultimately the operator's responsibility to ensure that personnels are notified, and steps are taken to convey this alert for appropriate action. While some incidents require little intervention, others may escalate to a call for evacuation of the facility. From process upsets to fire and gas detection alarm events to facility abandonment, it is essential that employees are notified in a clear, timely, and effective manor. The most prominent method in use today of facility-wide notification is an alarm broadcast over the public-address system in conjunction with associated visual and audible alarm devices. When a public-address system is tasked to perform this additional function, requirements for design, application, and installation then become regulatory and compliance issues     

Molecular simulation on the material/interfacial strength of the low-dielectric materials

In this paper, the material stiffness of amorphous/porous low-k material and interfacial strength between amorphous silica and low-k have been simulated by the molecular dynamics (MD) methods. Due to the low stiffness of the low-k material, the interfaces which include this material are critical for the most delamination and reliability issues around the IC back-end structure. MD simulation technique is applied to elucidate the crack/delamination mechanism at these critical interfaces. However, due to the amorphous nature of the low-k material (e.g., SiOC:H), the atomic modeling technique of the amorphous/porous silica is first established. Through the experimental validation, the accuracy of this amorphous modeling technique is obtained, and the results show that this algorithm can represent the trend of the mechanical stiffness change due to different chemical composition of low-k material. A novel interfacial modeling technique, which model the status of chemical bonds at interface during the delamination loading, is developed. Afterward, the simulation of the mechanical strength of the amorphous silica/SiOC:H interface, is implemented. The simulation depicts that the existence of the strong Si–O covalent bond will significantly enhance the adhesive strength of the interface. Instead of the covalent bond at interface, the simulation results also reveal the multiple atomic scaled crack path within the material during the interfacial delamination. Hence, improving the material stiffness of the soft low-k material and preventing the pore at interface can increase the adhesive strength of the silica/low-k interfacial system.