新型發光二極體封裝材料之開發：無機顆粒/矽樹脂複合材料之製備

Frequently, passive dry deposition collectors are used to sample atmospheric dust deposition. However, there exists a multitude of different instruments with different, usually not well-characterized sampling efficiencies. As a result, the acquired data might be considerably biased with respect to their size representativity, and as a consequence, also composition. In this study, individual particle analysis by automated scanning electron microscopy coupled with energy-dispersive X-ray was used to characterize different, commonly used passive samplers with respect size-resolved chemical and physical properties of mineral dust aerosol particles. In addition, computational fluid dynamics simulations were conducted to predict the deposition of particles on to different passive samplers and thereby to achieve deposition velocities from a theoretical point of view. Scanning electron microscopy (SEM) calculated deposition rate measurements made using different passive samplers show a disagreement among the samplers. Modified Wilson and Cooke (MWAC) and Big Spring Number Eight (BSNE) - both horizontal flux samplers - collect considerably more material than Flat plate and the Sigma-2, which are vertical flux samplers. The collection efficiency of MWAC increases for large particles in comparison to Sigma-2 with increasing wind speed, while such an increase is less observed in the case of BSNE. A positive correlation is found between deposition rate and PM10 concentration measurements by an optical particle spectrometer. The results indicate that a BSNE and Sigma-2 can be good options for PM10 measurement, whereas MWAC and Flat plate samplers are not a suitable choice. A negative correlation was observed in between dust deposition rate and wind speed. Deposition velocities calculated from different classical deposition models do not agree with deposition velocities estimated using computational fluid dynamics simulations (CFD). The deposition velocity estimated from CFD was often higher than the values derived from classical deposition velocity models. Moreover, the modeled deposition velocity ratios between different samplers do not agree with the observations. Results also show that mineral dust is found to be the dominating mineral particle type during this campaign, comprising of different classes of classes of silicates, quartz-like, calcite-like, dolomite-like and gypsum-like particles. In addition, the analysis clearly indicates that the composition of dust aerosol particles remains largely unaffected by the sampler type. By using the relative abundance of the particle groups, size-resolved complex refractive index of dust particles is calculated. It is found that average refractive index is mainly wavelength dependent. The calculated real part of refractive index varied in between 1.71 and 1.53 for wavelengths ranging from 370 to 950 nm. Likewise, the imaginary part of refractive index is calculated for iron oxide particles and is varied in between 3.28*10-4 to 7.11*10-5 for wavelengths in the range of 250-1640 nm. Additionally, the refractive index values have shown a slight decrease with particle size. In the study, the potential for buffering of dust aerosol particles on the acid mobilization of iron particles is also analyzed. From analysis, it is found that the buffering potential depends on the environmental conditions and time. Moreover, by analyzing the ratio of sulfate mass to the total mass of dust of individual particles with the particle sizes, the mixing state of sulfate particles in the total dust particles were investigated. The analysis indicates that the finer dust particles were associated with higher content of sulfur, while the coarse dust particles corresponds to lower sulfur contents revealing only fine mode sulfate is internally mixed with mineral dust aerosol particles. Overall, the results show that passive sampling techniques coupled with an automated single particle analysis could be a good option to assess physical and chemical properties of atmospheric mineral dust particles.

It was about 125 years ago that the light bulb was commercialized by Thomas Edison. No doubt a brilliant invention at the time, today its low power conversion efficiency is one of the reasons why lighting in the western world has such high energy consumption. Thus, the potential for saving energy is enormous in this area. The introduction of halogen, discharge and fluorescent lamps has lead to certain efficiency improvements, however more than half of the energy is still lost as heat. Light-emitting diodes (LEDs) are very promising candidates for high efficiency light sources, with modern devices showing internal quantum efficiencies of virtually 100 %. However, due to the high refractive index of the commonly used semiconductor materials it is very difficult to have a large extraction efficiency; in a standard cubic geometry most of the internally emitted light is trapped inside the device due to total internal reflection. Several methods have been developed in order to circumvent this problem, either by optimizing the device geometry in order to increase the escape cone or by incorporating a resonant structure in order to force the internal emission into the existing escape cone. The latter approach is called microcavity LED (MCLED) or resonant cavity LED (RCLED). In a MCLED the spontaneous internal emission is controlled by placing the emitter inside an optical cavity with a thickness of the order of its emitting wavelength. The resulting interference effects increase the part of the emission that can be extracted. Contrary to the other approaches this is possible without changing the device geometry and thus without additional costly back-end processing steps. The control of the farfield radiation pattern makes these devices particularly interesting for high brightness applications, which demand highly directional emitters, such as for printing, bar code reading, large area displays and optical communication. The extraction efficiency of a MCLED is inversely proportional to the effective cavity length. An ideal cavity, allowing an extraction efficiency close to unity, consists of a low refractive index material and has an optical length of λ/2. In contrast to this, to obtain high internal quantum efficiencies it is necessary to use high index cavities with an optical length of at least λ. It should be noted, that the large penetration depth of the optical field in the semiconductor-based distributed Bragg reflectors (DBRs) leads to a significant increase of the effective cavity length and thus further reduces the achievable extraction efficiencies. In this thesis novel concepts to reduce effective cavity lengths and therefore increase extraction efficiencies are implemented into standard MCLED structures. The phaseshift cavity principle whilst maintaining the electrical properties of a standard A cavity achieves optical properties approaching that of a λ/2 cavity. The use of AlOx instead of AlAs as the, low refractive index component in the DBRs leads to smaller penetration depths and a concomitant reduction of the effective cavity length. A similar effect can be obtained by combining a resonant cavity with a thin-film structure. Thanks to these design improvements, the external quantum efficiency of different types of MCLEDs was increased. Near infrared emitting InGaAs/GaAs MCLEDs including a phase-shift cavity were realized, as both bottom and top emitting structures. The external quantum efficiencies achieved for emission into air were 18 and 19 %, respectively. With the additional incorporation of an oxide based bottom DBR, the efficiency of top emitting near infrared MCLEDs was further increased to 28 %. Red emitting AlGaInP-based structures are not compatible with the phase-shift cavity principle. However the beneficial effect of the implementation of an oxide DBR is greater at their wavelength rather than in the near infrared. Thus with preliminary red emitting GaInP/AlGaInP MCLEDs containing a bottom oxide DBR external quantum efficiencies of 12% could be achieved. Unfortunately, the incorporation of an oxide DBR significantly complicates the device design and the device fabrication. These problems can be avoided by combining the resonant cavity with a thin-film structure instead. Initial non-optimized red emitting thin-film MCLEDs were realized by OSRAM Opto Semiconductors and characterized in this work. They show external quantum efficiencies of 23 % and 18 % with and without encapsulation, respectively. It is assumed that a significant fraction of the high external quantum efficiency is due to a strong photon recycling effect in these devices. Simulations presented in this thesis show that the theoretical limits for the MCLEDs discussed above are slightly higher than the values obtained, encouraging further device optimization. The thin-film MCLEDs seem to hold the biggest potential for high efficiency emission from MCLEDs, independent of the wavelength range of emission.

With the emergence of new color-mixing LED systems based on LED devices of different color temperatures, the need for a new modeling technique for LED systems with nonidentical LED devices becomes imminent. This paper presents a modeling tech- nique for LED systems with LED arrays comprising nonidenti- cal LED devices that have nonidentical optical-thermal-electrical properties. Based on a general 3-D photo-electro-thermal LED node model, LED devices of different kinds can be arranged in var- ious array forms according to their system construction and design. By linking the system matrix to the correlated-color-temperature prediction, the proposed modeling technique provides an accu- rate prediction of the temperature distribution, luminous flux, and correlated color temperature of the LED systems. The tempera- ture distribution and light output of the LED systems have been measured using an infrared imaging system and a spectrophoto- colorimeter with an integrating sphere. The modeling technique has been successfully demonstrated and experimentally verified on several LED systems comprising nonidentical LED devices. It is particularly useful as a modeling tool to study new color-mixing LED systems based on different types of LED devices. Index Terms—Correlated color temperature (CCT), light- emitting diodes (LED), lighting system, nonidentical LEDs, photo- electro-thermal (PET), thermal model.

Effect of thermal aging on the optical, dynamic mechanical, and morphological properties of phenylmethylsiloxane-modified epoxy for use as an LED encapsulant

Ambient temperature has a significant effect on the electrical and luminous parameters of light-emitting diodes (LEDs), which include forward and reverse current, forward voltage, and luminous flux. This paper gives insight into the influence of ambient temperature on the electrical and luminous parameters of LEDs powered by a rectangular pulsed voltage source versus those powered by a constant voltage source. The characteristics of LEDs in LED lighting devices were studied to determine their optimal operating conditions. To this end, rectangular pulse voltages with different pulse filling factors D were considered against the DC voltage source. Characteristics were obtained for the current stabilization mode and for the LED voltage stabilization mode. In both modes, the temperature dependence of the luminous flux, current, voltage, power consumption, and luminous efficiency of the LEDs was studied in the 20 °C to 60 °C range. The optimal LED operating conditions were determined, of which their luminous flux and luminous efficiency are least dependent on ambient temperature. When powered by a rectangular pulse voltage, the LED device drivers’ optimal pulse filling factor and operating frequency were determined.

Light emitting diode (LED) with a long lifetime, low power consumption, and low pollution has been successfully applied in many products. However, due to its low electro-optical conversion efficiency, high percentage of input power transformed to redundant heat, thus increasing the LED temperature. This phenomenon decreases the luminous flux, changing light color, and useful life span of LED. Therefore, thermal management becomes an important issue in high power LED. In this paper, the variation of luminous flux and light color for different LED lighting modules under long time operation has been measured and discussed. In addition, a detailed finite element model of LED lighting module, MR-16, with a corresponding input power and suitable boundary conditions is established by using the ANSYS finite element analysis program. Furthermore, to validate the simulation results, the current-voltage-temperature method for characterization of a diode is utilized to measure the junction temperature of LED chip indirectly and compare with simulation results. After the simulation is validated, various thermal performance assessments under the different design parameters of the LED package and lighting module are also investigated in this paper. The methodology and analysis results of this paper can provide a guideline for the LED lighting module such as MR-16 design in the future.

Light Emitting Diode (LED) luminaires are known to have higher efficacy compared to other types of light sources. Therefore, this type of luminaire has been deployed to replace existing conventional types of light sources as means of energy-saving around the world. LED efficacy is commonly measured using a photometer mounted in a goniophotometer or an integrating sphere system. However, due to the different spectral properties of the LEDs compared with the source used in the photometer calibration, mismatch correction needs to be applied in the measurement process. Due to the arduous process of obtaining the correction, the measurement of luminous flux using a spectroradiometer is proposed in this study. By utilizing this device, the mismatch correction does not need to be applied. The measurements of several commercially available LED and energy-saving compact fluorescent luminaires (CFL) show that current LED has twice the efficacy of the CFLs. The LED shows efficacy in the range of 114 lumen/watt. The measurement uncertainty associated with the efficacy of the LED is 4.2%. It is expected that the quality assurance and the accuracy of LEDs luminaires measurement and testing in Indonesia can be improved by using the integrating sphere with the spectroradiometer measurement method.

Thermal characteristics of light emitting diode (LED) devices directly effects on the luminous efficiency and long term reliability of LEDs. Junction temperature and thermal resistance are the main parameter that reflection of the heat dissipation capability of the LED device. In this study, relationships between thermal resistance and luminous flux and electrical power are simplified based on the photo-electrothermal theory. A new method using the optical-electrical characteristic of the LED is proposed to measure thermal resistance and junction temperature. The calculation of thermal resistance of the LED utilizes the reduction rate of luminous efficacy with the increasing temperature k e , heat dissipation coefficient k h , heat sink temperature T hs and the electric power corresponding to maximum luminous flux P d ∗. The thermal resistances of different brands and different power of LED devices are measured; the measuring results are highly consistent with nominal thermal resistance, which confirms the feasibility and generality of the proposed method. This method is simple and credible, and requires no expensive thermal measuring instruments, making it valuable for engineering application.

To meet the needs of ambient intelligence and the mimaturization of electronics, a MEMS/sensor package with exposed windows needs access to the environment. This presents a challenge for MEMS or sensor packaging/encapsulation. The exposed die and MEMS/sensor are brittle and can not withstand large stresses. By clamping a film around the chip's functional area, the surface of the chip is protected by film and the MEMS/sensors exposed window will be bleed and flash free. Relative to steel clamping force, the clamping force when using soft film is dramatically decreased. Film Assisted Molding (FAM) technology can meet the packaging demands of the MEMS and sensor functional opening area. FAM technology can fulfill the requirement of encapsulation of the advanced MEMS microsystems with low cost and excellent performance. Tiny exposed windows can be directly realized in the mold cap with film assisted transfer molding technology. This technology can be adopted to thru-mold vias for Package on Package (PoP) applications. Film assisted technology also opens the opportunity of wafer level transfer molding with an exposed window. The increasing demand for light emitting diodes (LEDs) has been driven by many applications, including communications, signage and large power solid state lighting (SSL). The LED encapsulation can be implemented by film assisted molding technology in die, package and module level. High power Solid state lighting (SSL) is a new promising lighting technology based the brightness light emetting diode (LED), which is promising to replace the conventional light sources for its economic and environmental saving. The encapsulation of SSL at die and module level is a challenge with low costs and high efficiency thermal management.

Improving the efficiency of light extraction is important for the fabrication of high-power white light-emitting diodes (LEDs) with high luminous flux. This article reports on the development of a method for increasing the efficiency of photon extraction in LEDs with phosphor conversion. The presented method is based on the fact that the phosphor layer that converts the emission spectrum of the LED has a three-dimensional structure in the form of pyramids, which allows us to utilize the radiation lost inside the LED by redirecting it to the output. The optical and electrical parameters of the LEDs obtained using this method are studied experimentally. A three-dimensional model of the LED under investigation was built using the SOLIDWORKS software. Monte Carlo ray tracing simulation was performed in Zemax OpticStudio. The experimental data were compared with the data obtained through the simulation.

The development of light-emitting diode (LED) technology has resulted in widespread solid state lighting (SSL) use in consumer and industrial applications. Previous researchers have shown that LEDs from the same manufacturer and operating under same use-condition may have significantly different degradation behavior. Applications of LEDs to safety critical and harsh environment applications necessitate the characterization of failure mechanisms and modes. This paper focuses on a prognostic health management (PHM) method based on the measurement of forward voltage and forward current of bare LED under harsh environment. In this paper, experiments have been done on single LEDs subjected to combined temperature–humidity environment of 85 °C, 85% relative humidity. Pulse width modulation (PWM) control method has been employed to drive the bare LED in order to reduce the heat effect caused by forward current and high frequency (300 Hz). A data acquisition system has been used to measure the peak forward voltage and forward current. Test to failure (luminous flux drops to 70%) data has been measured to study the effects of high temperature and humid environment loadings on the bare LEDs. A solid state cooling method with a Peltier cooler has been used to control the temperature of the LED in the integrating sphere when taking the measurement of luminous flux. The shift of forward voltage forward current curve and lumen degradation has been recorded to help build the failure model and predict the remaining useful life (RUL). Particle filter has been employed to assess the RUL of the bare LED. Model predictions of RUL have been correlated with experimental data. Results show that prediction of RUL of LEDs, made by the particle filter model, works with acceptable error-bounds. The presented method can be employed to predict the failure of LED caused by thermal and humid stresses.

We demonstrated tomographic phase microscopy (TPM) of living diatoms in liquid in order to quantitatively analyze localization of cell components of symmetric shape cells. One TPM image includes several millions of pixel data of three-dimensional optical information such as refractive index (RI) values of cell components. In this work, the obtained TPM data of living cells were analyzed using X–Y cross sections to visualize the localization of cell components. Distribution of RI values at the cell surfaces and inside the cells were quantified. The results showed that the RI values were slightly lower at the cell center (RI ∼ 1.400) than the cell boundary (RI ∼ 1.420). RI values were fluctuated according to the depth measured from the cell surface also. Furthermore, statistical analysis by root mean square and Moran's I methods revealed unique localization of RI values for several cells among 25 individuals. In addition, the volumes of the cells estimated using TPM data corresponded to the cell volumes obtained via scanning electron microscopy. Our work proposed an effective procedure to quantitatively/statistically investigate intracellular materials of living cells based on physical information of TPM data.

We have demonstrated that a phosphor conversion (PC) white light-emitting diode (LED) light source composed of multi-layered (ML) red, green, and blue (RGB) phosphors with a near-ultraviolet (n-UV) LED as an excitation source shows excellent color rendering, luminous efficacy, and luminous flux. The ML-phosphor structure consists of vertically stacked layers and could significantly reduce cascade excitation loss compared with a mixed RGB PC white LED. A high luminous efficacy of 82 lm/W with a high color-rendering index (CRI) of over 90 was achieved using a ML-RGB PC white LED. The ML-RGB structure also enables a white LED with an ultrahigh CRI of 99 and a high luminous efficacy comparable to that of a high CRI fluorescent lamp. We have also fabricated a high-power ML-PC white LED excited by an n-UV LED. In one package, a high luminous flux of 61 lm at a high CRI of 94 was obtained.

Compared with incandescent lamps and fluorescent lamps, nowadays LEDs (Light Emitting Diodes) are power saving, environment-friendly, and have the advantages of long lifetime and flexible color output. Therefore, LEDs are being widely used in many fields. In this paper, three high-power LEDs packaging modules with different packaging structures were selected to do the performance analysis based on the experiments. In the measurement, the LED junction temperature was controlled at seven levels (25°C, 50°C, 65°C, 75°C, 85°C, 95C, 100°C) in sequence. The thermal variation of some photoelectric parameters for LED packaging modules, such as forward voltage, relative flux output, correlated color temperature (CCT), color rending index (Ra), luminous efficiency and spectrum, were focused on and analyzed here. The experimental results demonstrated that the luminous flux, luminous efficacy and forward voltage of LEDs decreased with the increase of the junction temperature, but these three LEDs packaging modules have different varieties on CRI, CCT and spectrum. The related reasons were analyzed briefly in this paper.

Refractive index is one of the most important physical parameters of the materials. Owe to its great influence on the working characteristics of an optical systems, high accuracy measurement is required. Many methods have been proposed such as the v-prism method, the minimum deviation angle method, and the interferometric method. However, for the restriction of the principle, the shape of the sample is required to be a parallel plate or a prism with a specific shape. The sample with only spherical or aspheric surfaces cannot be tested. In this paper, an improved Brewster method is proposed to measure the refractive index of optical materials with arbitrary shapes. Brewster law can be expressed as that the reflectivity of the P-polarized light approaches zero when it is incident in the Brewster angle, which is the inverse trigonometric value of the refractive index. In the original method, a parallel laser beam with P polarization is incident on the sample, and reflected by it to a photodiode to get the intensity. The minimum intensity position corresponding to Brewster angle can be found by changing the incident angle. The reflecting surface of the sample need to be planar to provide smooth reflective area with a size greater than the beam diameter. In the improved method, a laser probe focusing on the sample and an array detector are used instead of the parallel beam and the photodiode. The minimum intensity position can be found with image processing technology. Since the laser beam is focused on the sample, only a tiny area with a size of 10 microns for reflection is needed. Thus, whatever the shape of the sample is, the method can be used. In order to demonstrate the feasibility, samples with different shapes such as a prism, a parallel plate and a lens was tested, and the accuracy of the results could all reach the order of magnitude of 10-3.