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Light efficiency of chip-on-board light-emitting diodes (COB-LEDs) is much lower than the single-chip packaging LEDs due to its flat phosphor layer, and hemispherical phosphor layer realization is a great challenge in COB-LEDs packaging due to the low surface tension of the phosphor gel. In this paper, we demonstrated a facile method to fabricate patterned surfaces to deal with this challenge. First,...
In our previous study, we demonstrated a remote phosphor coating method by lens wetting for pcLEDs. For the proposed method, the phosphor gel droplet is dropped onto the concave inner surface of a hemispherical lens, then the phosphor gel wets the lens surface driven by gravity and surface tension and finally reaches to a stable geometry. In this study, fluid flow simulations based on Volume of Fluid...
Die attach process is widely used to realize the connection between the die, the device and the rest of the system in electronic packaging. In die attach process with solder, the reflow is necessary. During this process, the die moves under the action of capillary force induced by the liquid solder. A common phenomenon, die tilt usually occurs and strongly worsens the reliability and performance of...
In the conventional freeform lens design, people usually assume the inner surface as hemispherical and only the outer surface is designed. An important design degree of freedom on the inner surface is abandoned. In this study, by distributing the deviation angle, we proposed a method to design the inner and outer surfaces of freeform lens simultaneously. Detailed design method was presented and several...
Die attach process is widely used to realize the connection between die, device and the rest of the system in electronic packaging. During this process, the die moves under the capillary force induced by the liquidus solder. Such a die tilt phenomenon usually occurs and strongly worsens the reliability and performances of devices. In this paper, we built a numerical model based on fluid minimal free...
Simple experiments were conducted to obtain surface and lamp hold temperatures of a main-stream 4W LED bulb, which is on sale in the market. Two kinds of thermal calculations were also done based on the data from measurements. The total heat dissipation rates in those two thermal calculations are close to each other, which demonstrate that the thermal calculation is feasible for thermal analysis of...
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