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An innovative sensitive test method is developed to detect solder joint cracking for high power LED packages. The method is based on transient thermal analysis and can replace the dominating Light-On test. Test groups of LED packages were soldered with two different lead free solders (SnAgCu 305 and Innolot FL-640) on Aluminum Insulated Metal Substrate and exposed to temperature cycles. Transient...
We report on the thermal analysis of high-power LED arrays used for solid state lighting (SSL). Variety of assemblies using high-power LED chips, were considered along with different heat-sink designs. Chip-on-plate (COP) packaging technique was used for all the LED chips attached to variety of heat-sinks. The 3D modeling and simulations were carried out to study the thermal behavior of LED chips...
Flip chip technology is one of the advanced chip packaging techniques in IC packaging industry. This technology may provide a solution to enhancing heat-dissipation and optical performance of the LED when applying to the LED packaging. The goal of this study is to experimentally and numerically study the thermal performance of flip-chip (FC) LED (with the size of 1 × 1 mm) with and without underfills,...
It's proved that the physical meaning of the electrical average temperature rise of series LED array system tested by electrical temperature sensitive parameter (TSP) method is the arithmetic mean of the temperature rises of all sub-LEDs in the system. Based on this relationship, a novel method to evaluate the temperature distribution of series LED systems by scan measurement and recursive calculation...
This paper aims at providing a rigorous description of the thermal impedance of AC LEDs, especially of retrofit LED lamps which are directly driven from the mains supply. The paper gives an overview of the different representations of the thermal impedance then provides estimates of the AC power of LEDs for two extreme cases (voltage and current driven situations). The high harmonic content of the...
In this paper, the thermal analysis is carried out by the combination of actual thermal measurement and numerical finite element simulation to investigate insightfully the thermal characteristics of each element in the whole assembly of the LED lighting system (LLS). Based on the thermo/fluid coupled field numerical simulation, the ANSYS??,s finite elements are used to model the detailed assembly...
We studied the thermal properties LED light unit composed of nine LED chips in a MLCMP (multi-layer ceramic-metal package) and compared various thermal dynamic models. We concluded that the direct measurement of forward voltage Vf is the most practical approach for in-situ testing. By calibrating the Vf to junction temperature Tj at various forward current in a temperature controlled oven, the linear...
Nowadays the demand for thermal standards for power LEDs is increasing. On the one hand metrics for fair comparison of competing products are needed; on the other hand, designers of power LED-based applications demand reliable and meaningful data for their daily work. Today's data sheet information does hardly meet any of these requirements. In earlier papers we compared the current situation in the...
Wafer-level packaged light-emitting diodes (LEDs) are useful for the high-power applications such as back light unit and general solid-state lighting due to the compactness and integrated fabrication process. In this letter, wafer-level packaged LEDs with red, green, and blue multichips were fabricated, and the thermal characteristics of wafer-level packaged LEDs with multichips such as thermal resistance...
The present work aims at studying the cooling performance of a thermoelectric device that integrated with integrated heat spreader (IHS) on a flip-chip plastic ball grid array (FC-PBGA) package. The new thermoelectric device herein is fabricated on the metal substrates by flip-chip assembly process. Thermal performance of the new package was comprehensive studied. The thermal resistances of IHS with/without...
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