Light Emitting Diode Package Research Articles

Dynamic prediction of optical and chromatic performances for a light-emitting diode array based on a thermal-electrical-spectral model.

Light-emitting diode (LED) arrays have attracted increased attention in the area of high power intelligent automotive headlamps because of their superiority in disposing of the power limit of an individual LED package and controllably luminous intensity and illumination pattern. The optical and chromatic performances of an LED array do not equal to the sum of individual LED packages' performances, as the thermal interactions between individual LED packages can't be ignored in the actual application. This paper presents a thermal-electrical-spectral (TES) model to dynamically predict the optical and chromatic performances of the LED array. The thermal-electrical (TE) model considering the thermal coupling effect in the LED array is firstly proposed to predict the case temperature of each individual LED package, and the Spectral power distributions (SPDs) of individual LED package is then decomposed by the extended Asym2sig model to extract the spectral characteristic parameters. Finally, the experimental measurements of the designed LED arrays operated under usage conditions are used to verify the TES model. Some validation case studies show that the prediction accuracy of the proposed TES model, which is expressed as a quadratic polynomial function of current and case temperature, can be achieved higher than 95%. Therefore, it can be concluded that this TES model offers a convenient method with high accuracy to dynamically predict the optical and chromatic performances of LED arrays at real usages.

Enhanced emission of Eu3+ in lutetium tungsten molybdenum oxide phosphors: Synthesis, optical properties, thermal behavior, and LED packaging

By adjusting molar ratios of raw materials of Lu2O3 (Eu2O3) to WO3 and MoO3 as well as WO3 to MoO3, several lutetium tungsten molybdenum oxide phosphors Lu2W0·5Mo0·5O6, Lu2WxMoyO9 (x + y = 2), Lu2W1·5Mo1·5O12, and Lu6W0·5Mo0·5O12 were synthesized through a solid-state reaction method. The materials were characterized by X-ray diffraction (XRD) patterns, scanning electron microscope (SEM) images, energy-dispersive spectra (EDS), diffuse reflection (DR) spectra, room temperature photoluminescence (PL) excitation and emission spectra, luminescence decay curves, and temperature dependent PL spectra. Red shift excitation bands were recorded in Lu2WxMoyO9 (x + y = 2) phosphors with the concentration of Mo6+ increasing. Enhanced Eu3+ excitation and emission spectra were observed in the Lu2WxMoyO9 (x + y = 2) phosphors with the concentration of W6+ increasing. Possible energy transfer processes were proposed to explain the PL excitation and emission spectra. By combining phosphors with 365 nm ultraviolet (UV) chips, the obtained light emitting diodes (LEDs) gave bright red light under forward bias current. The results suggest that the obtained Eu3+ doped Lu2WMoO9 have potential applications in phosphor converted based UV LEDs.

Synthesis, optical properties, energy transfer, thermal behavior, and LED package of Eu3+ doped lutetium tungsten oxide phosphors

By using a solid-state reaction method, Eu3+ doped monoclinic phase of Lu2WO6, mixture of Lu2WO6 and Lu2W3O12, Lu2W3O12, and hexagonal phase of Lu6WO12 lutetium tungsten oxide phosphors were synthesized. The obtained phosphors were composed of micrometre or nanometre scale particles. The energy-dispersive spectra (EDS) illustrated that the W atom percent increased with the sequence of Lu6WO12, Lu2WO6, mixture of Lu2WO6 and Lu2W3O12, and Lu2W3O12. The diffuse reflection (DR) spectra presented the broad absorption bands in the ultraviolet wavelength range and the energy gap values were evaluated based on the DR spectra. The photoluminescence (PL) excitation and emission spectra illustrated that the Lu2WO6 presented the most intense PL intensities in the four phosphors and the optimal Eu3+ concentration was 20 mol% in Lu2WO6 phosphors. The 20 mol% Eu3+ doped Lu2WO6 phosphor presented good thermal stability and kept 85% intensity of 50 °C at 200 °C. The deduced lifetime of Eu3+5D0→7F2 transition was several hundred micro-minutes. The energy transfer processes and the energy transfer efficiency were analysed based on the energy level diagram and the PL emission spectra. The obtained red phosphor was packaged into 308 nm chips and red light-emitting diodes (LEDs) were obtained. The chromaticity coordinates and the color purity were measured to evaluate the packaged LED devices. The results suggest that the Eu3+ doped Lu2WO6 has good thermal stability and has potential applications in phosphor converted LEDs.

Effect of niobium pentoxide (Nb2O5) on the microstructure and properties of the diopside glass-ceramics produced from Bayan Obo mine tailing

Diopside (CaMgSi2O6) glass-ceramic, a typical derivative of the pyroxene system, has attracted considerable attentions in the fields of anti-erosion, anti-abrasion, light-emitting diode (LED) packaging, or electric circuit substrate materials because of its high mechanical strength, good physical and chemical stability, as well as remarkable low dielectric coefficient and loss. However, the effect of niobium pentoxide (Nb2O5) on the microstructure and property of this technically important glass-ceramic is still not fully understood. Therefore, diopside glass-ceramics with 0 wt%, 0.1 wt%, 0.025 wt%, 0.5 wt%, 1 wt%, 2 wt%, and 4 wt% of Nb2O5 were synthesized respectively by the traditional melting method using Bayan Obo mine tailing and fly ash as the main starting materials. The obtained materials were studied by differential scanning calorimetry, X-ray diffractometry, Raman spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, mechanical property, and dielectric property measurements to reveal the effect of Nb2O5 on its microstructure and property. The result shows the addition of Nb2O5 has a clear effect on increasing the formation of diopside crystals and the crystallization of calcium niobate (Ca2Nb2O7) secondary phase at the intergranular areas between diopside crystals. And this latter microstructural change relates closely with the decrease in the average size of diopside crystals and their morphology changing from the ones resembling chrysanthemum flowers to clusters of roughly round islands. Addition of Nb2O5 up to 2 wt% exhibits a near monotonous effect on improving the bending strength. The maximum value of it can reach as high as 236 MPa. The dielectric constant rises from 7 to 9.7 with the increase of Nb2O5 addition from 0 to 4 wt%, while the dielectric loss fluctuates within the range of 0.015 to 0.035. The comparison of the results of this study with those of peers showed the crystallization of diopside crystals was more likely enhanced through the mechanism related to the Nb2O5-induced phase separation in the base glass rather than the normally reported heterogeneous nuclei mechanism reported for Ferric oxide (Fe2O3), chromium trioxide (Cr2O3), and titania (TiO2).

Penetrating Biological Tissue Using Light-Emitting Diodes with a Highly Efficient Near-Infrared ScBO3:Cr3+ Phosphor

Recently, infrared (IR) light-emitting diodes (LEDs) have attracted considerable interest in the research field worldwide. IR phosphors, the basic materials utilized in LEDs, have become a research hotspot as well. Here, we introduce the high-quantum-efficiency IR ScBO3:Cr3+ phosphor, which provides a spectral range of emission from 700 to 1000 nm with a peak maximum at 800 nm. Electron paramagnetic resonance spectroscopy, with high element selectivity, was used to elucidate the unusual small peak in the photoluminescence spectrum. Phonon structure and electron–lattice interaction were well observed and discussed via temperature-dependent measurements. Moreover, the high quantum efficiency of 72.8% was achieved. To evaluate their potential practical application, phosphor-converted LED packages were designed, which revealed high stability and high output power of 39.11 mW. Furthermore, the fabricated IR LED demonstrated a remarkable ability to penetrate biological tissues. This study provides insights into the luminescent properties and the practical applications of IR LEDs.

Performance Comparison of InGaN-Based Phosphor Converted and AlGaInP-Based Red Light-Emitting Diode Packages for Vehicle Rear Fog Lamps

We investigated the electrical and optical properties of chip LED and phosphor-converted red LED (pcR-LED) packages for a vehicle rear fog lamp application. The chip LED package had a lower forward voltage, narrower electroluminescence spectrum, and a larger view angle than the pcR-LED package. At 85 °C under 700 mA, the pcR-LED package emitted 26.8% more luminous flux than the chip LED package. After 1000 temperature cycles (−40 to +125 °C), the chip LED packages exhibited a 7.83% maintenance rate variance, whereas the pcR-LED packages showed a 2.78% change. Furthermore, after 1000 h under relative humidity conditions of 85 °C/85% both the samples demonstrated an average maintenance rate >98.66%. At 85 °C under 700 mA, it was demonstrated that the pcR-LED package exhibited a 48.9% lower thermal resistance (junction to package) than the chip LED package. Also for the chip LED package, the temperatures were 58.6 °C at the central region and 61.9 °C at its periphery, whereas the pcR-LED package had temperatures of 70.5 °C at the center and 55.8 °C at the periphery. Unlike the chip LED package, neither current nor temperature significantly affected the CIE coordinates of the pcR-LED packages.

The interface adhesion of CaAlSiN3: Eu2+ phosphor/silicone used in light-emitting diode packaging: A first principles study

The CaAlSiN3:Eu2+ red phosphor and its silicone/phosphor composite are very promising materials used in the high color rendering white light-emitting diode (LED) packaging. However, the reliabilities of CaAlSiN3:Eu2+ and its composite are still being challenged by phosphor hydrolysis at high humidity application condition. A fundamental understanding of the interface adhesion between silicone and CaAlSiN3:Eu2+ is significant for the developments and applications of this material. In this work, the mechanical properties of silicone/pristine CaAlSiN3:Eu2+ and silicone/hydrolyzed CaAlSiN3:Eu2+ composites are experimentally measured and compared firstly, in which both the tensile strength and Young’s modulus of composite are increased after the hydrolysis reaction. Then, the first principles Density Functional Theory (DFT) calculations are used to investigate the adhesion behaviors of the silicone molecular on both the pristine and the hydrolyzed CaAlSiN3[0 1 0] at atomic level. The results show that: (1) The silicone molecular is weakly adsorbed on the pristine CaAlSiN3[0 1 0] via Van der Waals (vdW) interactions, while silicone molecular is much stronger absorbed on the hydrolyzed CaAlSiN3[0 1 0] due to the formation of hydrogen bonding at the interface; (2) The transient state calculations indicate that the sliding energy barrier of silicone on the hydrolyzed CaAlSiN3[0 1 0] is higher than that on the pristine one, as the increased adsorption energy and surface roughness. Generally, the findings in this paper can guide the phosphor selection, storage and process in LED packaging, and also assist in improving the reliability design of LED package used in high moisture condition.

White LEDs With High Optical Consistency Packaged Using 3D Ceramic Substrate

Packaging efficiency and optical performances are important indexes for white light-emitting diodes (WLEDs) packaging. In this letter, wafer-level WLEDs packaging were presented by printing phosphor on three-dimensional (3D) ceramic substrate to improve packaging efficiency and optical consistency. The 3D ceramic substrate was prepared by repeatedly electroplating copper cups on the planar direct plated copper (DPC) ceramic substrate. The phosphor concentration was adjusted to realize natural white light. The fabrication errors of the 3D ceramic substrate and the optical performances of WLED modules were analyzed to evaluate the optical consistency of the WLED modules packaged by using 3D ceramic substrate. Consequently, the fabrication errors of 3D ceramic substrate are less than 1%. When the phosphor concentration was set at 12.5 wt%, the packaged LEDs achieve a natural white light with luminous efficiency (LE) of 94.55 lm/W, correlated color temperature (CCT) of 5915 K, and chromaticity coordinate of (0.3166, 0.3345). The WLED modules exhibit small standard deviations in LE (1%), color rendering index (1%), correlated color temperature (98 K), and high reliability. The results indicate that the WLEDs packaged using 3D ceramic substrate have excellent optical consistency.

Improvement in the Reliability of AlGaInP-Based Light-Emitting Diode Package Using Optimal Silicone and Leadframe Structure

We investigated how the reliability of red light-emitting diode (LED) packages was affected by the types of silicones and package structures. The tensile strengths of different types of silicones varied from 3.2 to 8.1 MPa and their elongations were in the range of 40–150%. To characterize the output maintenance of packaged LEDs, the packages were kept under an 85°C/85% relative humidity (RH) condition for 72 h, which was then reflow-processed at 260°C three times. The output powers of the samples were degraded by 1.27–21.2% after the process, depending on the types of silicones. Only the sample LD-B experienced cracking. The effect of four different leadframe structures on the reliability of the sample LD-B was characterized. After the thermal treatments, the sample with 4 leads (circular window) suffered cracking. Simulations showed that unlike the others, the sample LD-B displayed additional stress concentrator at the centre of the silicone encapsulant. The spray-coating test revealed that moisture was permeated mainly through the Polyphthalamide (PPA)/silicone interfaces. These results show that use of silicone with high tensile strength, spray-coating, and optimized leadframe structure can be effective in achieving the high moisture reliability of red-LED packages.

Hydrolysis kinetic study of CaAlSiN3:Eu2+ red phosphor with both water immersion test and first-principles calculation

At present, most high-power white Light-emitting diode and laser diode (LED&LD) package is usually constructed by a blue LED&LD chip with a Cerium doped Yttrium Aluminum Garnet (YAG:Ce3+) yellow phosphor, but its color rendering performance is severely challenged due to the lack of red light emission spectrum. The CaAlSiN3:Eu2+ red phosphor can effectively improve the color quality of traditional yellow phosphor converted white LED&LDs(pc-wLED&LDs), however, it is often susceptible to degradation under high temperature and high humidity environments, which will directly affect the color quality of pc-wLED&LDs. In this study, a series of water immersion tests on CaAlSiN3:Eu2+ red phosphor are used to quantitatively study its hydrolysis reaction kinetics. Then, the degradations of its photoluminescence and photothermal performances are evaluated by characterizing the crystal structure, micromorphology and chemical element composition. Finally, an atomic level hydrolysis reaction mechanism of CaAlSiN3:Eu2+ red phosphor is investigated by using the first-principles density functional theory (DFT) calculation. The results show that: (1) By modelling the in-situ monitored electrical conductivity of CaAlSiN3:Eu2+ red phosphor water solution with a first-order reaction function, the calculated hydrolysis reaction rate satisfies the Arrhenius relationship and the reaction activation energy is estimated as 49.19 kJ/mol; (2) The increased self-heating effect of CaAlSiN3:Eu2+ red phosphor after water immersion test attribute to its drastic drop of light emission efficiency; (3) The hydrolysis reaction mechanism of CaAlSiN3:Eu2+ red phosphor is confirmed, which sequentially results in the dissolution of Ca2+ and OH−, the crash of host lattice and the accumulation of reaction residues.

Effects of humidity and phosphor on silicone/phosphor composite in white light-emitting diode package

Silicone/phosphor composite, which serve as mechanical protection and light conversion material, is an integral part of white light-emitting diode (LED) package. In this paper, a comprehensive study is conducted to investigate the effect of humidity and phosphor on moisture absorption, hygroscopic swelling, mechanical behavior, as well as thermal properties of silicone/phosphor composite in comparison with the pure silicone. SEM/EDAX and FTIR were performed to identify the phosphor and silicone compositions. Through moisture sorption test, it has been observed that the addition of phosphor significantly lowers the capacity of moisture absorption, but accelerates the diffusivity of moisture absorption. The hygroscopic swelling test showed that the phosphor has little effect on the swelling compared to the pure silicone sample. Both moisture absorption/desorption and hygroscopic swelling/de-swelling are reversible. Strain ramp test revealed that the phosphor enhances the stiffness of the composite. The moisture absorption, however, has negligible impact on mechanical stiffness for both pure and composite samples. Finally, thermal expansion test showed that the coefficient of thermal expansion does not change with the addition of phosphor into pure silicone.

Microstructure and thermal conductivity of AlN coating on Cu substrate deposited by arc ion plating

Heat dissipation is crucial to efficient light emitting diode (LED) packaging, and thermal management material determines the heat dissipation. In this study, AlN coating was deposited on Cu substrate via arc ion plating (AIP) to replace traditional ceramic substrates or epoxy resin-coated metal substrates. The morphology, phase structure, chemical composition, hardness, and thermal conductivity were investigated as a function of deposition parameters of bias voltage and nitrogen pressure. As the bias voltage increases, the quantity of macroparticles in the AlN coating is reduced, while the hardness initially increases and then decreases. With increasing nitrogen pressure, the hardness of the AlN coating increases because the formation of AlN phase is enhanced and the coating becomes more compact. The thermal conductivity of the AlN/Cu sample is reduced by just 2.6% compared with the Cu substrate, suggesting slight effect of the AlN coating on thermal conductivity of the AlN/Cu structure. The results show that the AlN-coated Cu substrate has a good application prospect in the field of LED packaging.

Effect of substrate temperature deposition on the thermal and optical performance of ZnO thin films as thermal interface material

ZnO thin films were deposited onto aluminium substrates at different substrate temperatures from 300 to 450 °C by chemical vapour deposition method using zinc acetate dihydrate as precursor. The effects of substrate temperatures on the thermal and optical performances of a light emitting diode package were investigated. The thermal transients show that thin film deposited at 400 °C has the lowest thermal resistance and junction temperature with a different difference of 1.3421 K/W and 2.7 °C respectively. The correlated colour temperature of the LED interfaced with ZnO prepared at 400 °C showed a good agreement with the thermal performance and exhibited the lowest correlated colour temperature as the driving current increases. The luminance shows that bare Al demonstrate the lowest luminosity compare to the coated thin film as TIM. The excess heat that trapped within the air gaps affects the heat flow. This eventually affects the luminosity of the LED. Furthermore, the AFM measurements of CVD 3 (400 °C) samples show low roughness values which contribute to good thermal resistance and junction temperature values. Overall, the present study shows that the performance of the LED has been enhanced with ZnO thin film used as TIM.

A review of blue light emitting diodes for future solid state lighting and visible light communication applications

Abstract This paper reviews the rapid progress being made in the developments of organic/inorganic blue light emitting diodes (LEDs). Blue LEDs exhibits outstanding electrical and optical properties such as low forward driving voltage, high light output power, high brightness and high internal quantum efficiency (IQE). This article highlights the rapid advancements being made in the developments of organic/inorganic blue LEDs over the last five decades, efficiency enhancement techniques, efficiency droop in blue LEDs and the techniques to alleviate efficiency droop, recent developments in flexible blue LEDs, degradation mechanisms and reliability issues in blue LEDs, challenges in fabrication and packaging of blue LEDs and it also throw light on the applications of blue LEDs. Their uniqueness in terms of low forward driving voltage, high light output power and brightness and large modulation bandwidth has fuelled the incorporation of blue LEDs in a wide variety of applications such as visible light communication (VLC), solid state lighting (SSL), cellular phone displays, liquid crystal display backlights, flexible flat panel displays, outdoor full colour displays, indicators, smart TVs, projection displays and implantable biomedical devices.

Study on Reabsorption Properties of Quantum Dot Color Convertors for Light-Emitting Diode Packaging

Abstract Quantum dot (QD) attracts great attention in light-emitting diode (LED) packaging for high-quality light sources, while it leads to low light efficiency due to the significantly high reabsorption loss between QDs. Accordingly, we experimentally study the reabsorption properties of QD color convertors (QCCs) for LED packaging considering various thicknesses and concentrations under different injection current. The results indicate the QCC configuration with a small thickness and large concentration can have the same absorption ability for chip light as that with the opposite configuration, resulting in the same QD light proportion. However, the QCC configuration having smaller thickness is more useful to decrease the reabsorption loss, leading to higher radiant power (an increase of larger than 37.2%). Moreover, it is essential to gain a high radiant power of QD light with small reabsorption loss, which can be realized by combining QCCs with a low QD content and a source with a large injection current. Based on this simple and effective approach, a conversion loss smaller than 20%, close to their quantum yield, can be achieved, which is approximately four times smaller than that gained by QCCs with a high QD content. However, it introduces additional radiant power of chip light, suppressing further improvement in the QD light proportion. Much work is still required to make full use of the redundant chip light. This study provides a better understanding of the reabsorption properties of QCCs and can significantly accelerate their applications in illumination and display applications.

Progress and Perspective of Near-Ultraviolet and Deep-Ultraviolet Light-Emitting Diode Packaging Technologies

Abstract Ultraviolet light-emitting diodes (UV-LEDs) have drawn considerable attention in environment, life science, and industry fields, such as the applications of near UV-LEDs in resin curing, illumination, and identification, and deep UV-LEDs in disinfection, medical treatment, and biochemical inspection. However, due to the limitation of packaging technology, UV-LED devices exhibit low light efficiency and poor reliability compared with visible LEDs. The organic encapsulation materials are prone to UV aging, thermal degradation, and nonairtightness, which significantly reduce the performances of UV-LEDs. In order to solve this issue, UV-LED packaging technology has been proposed for UV-LED devices instead of conventional LED packaging. In this review, we investigated in detail the overview and challenges of near-ultraviolet light-emitting diodes (NUV-LED)/deep-ultraviolet light-emitting diodes (DUV-LED) packaging. For the packaging of UV-LEDs, all inorganic encapsulation materials, hermetic packaging structures with low-temperature bonding, reduced reflection losses, UV stable and transparent materials, and effective thermal management are key progresses to enhance the light efficiency and reliability of UV-LEDs. In addition, the summary and perspectives of NUV-LED/DUV-LED packaging were introduced and discussed.

Thermal Analysis and Performance Optimization of Quantum Dots in LEDs by Microsphere Model

Quantum dots (QDs) have aroused intensive research interest because of their unique optical properties and capability in the fabrication of high-performance light-emitting diodes (LEDs). However, the optical performance of the QDs is strongly affected by their intrinsic thermal sensitivity as well as the dispersion state in LEDs, thus demanding more accurate thermal control of the QDs in the LED package to promote performance optimization. In this article, a microsphere model is developed to study the thermal behavior of the QDs in the LED package by considering their monodispersion and heat accumulation. The utilization of the model provides the simulated temperature as well as the heat distribution of the QDs more in line with the experimental results, achieving an average error of only 0.01%-2%. Further study based on the microsphere model reveals that a layered package structure can offer better heat control and light uniformity for the QDs-based LEDs (QD-LEDs). The optimized package realizes a maximum of 12.5 °C temperature reduction for QDs than the conventional structure and the valid operation power for QD-LEDs to operate at 80 °C is promoted by 25%.

Integrated microsensor for precise, real-time measurement of junction temperature of surface-mounted light-emitting diode

Light-emitting diodes (LEDs) are widely used in many industrial applications owing to their high performance and efficiency compared with conventional lighting systems. However, a considerable amount of input power is inevitably dissipated into heat at the LED junction, which can degrade the performance and reliability of the LED; thus, it is important to monitor the change in the junction temperature of the LED. In this study, we present a micro-temperature sensor-integrated surface-mounted device (SMD) for accurate and real-time measurement of the junction temperature of an LED. The LED is mounted on a microfabricated Pt sensor in a similar way to the typical SMD assembly. The heat generated at the LED junction is conductively transferred to the microsensor, increasing the temperature and changing its electrical resistance. In contrast to the conventional techniques for thermal characterization of LEDs, the integrated microsensor provides real-time information on the junction temperature with high precision, reproducibility, and simplicity. Additionally, the temperature of the solder, which is not easily accessible but is closely related to the reliability of the LED, can be estimated by analyzing the thermal resistance of the LED package. Experimental and numerical results indicate a linear correlation (R2 = 0.988) between the junction and sensor temperatures, which is practically useful for the thermal management of the miniaturized SMD-LED.

High Moisture Accelerated Mechanical Behavior Degradation of Phosphor/Silicone Composites Used in White Light-Emitting Diodes.

In a high-power white light emitting diode (LED) package, the phosphor/silicone composite is typically used for photometric and colorimetric conversions, ultimately producing the white light. However, the phosphor/silicone composite is always exposed under harsh environments with high temperature, high blue light irradiation and high moisture when the LED operates. Therefore, its reliability issue has become one of the critical bottlenecks to improve the lifetime of a high-power white LED package. As the curing process and mechanical behavior of phosphor/silicone composite essentially determine its reliability, this paper firstly uses an in situ viscosity monitoring approach combined with Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FTIR) analysis to explain the curing mechanism of a phosphor/silicone composite by taking the effects of temperature and phosphor mass fraction into consideration. Then, the mechanical properties of phosphor/silicone composites aged under a long-term high moisture condition are evaluated by using the tensile test. Meanwhile, the finite element (FE) simulations, the Mori–Tanaka theoretical estimations and the microstructure analysis are applied to investigate the high moisture induced degradation mechanisms. The results show that: (1) the in situ measured isothermal viscosity curves of both pristine silicone and phosphor/silicone composites follow the Arrhenius empirical model, and high temperature and high phosphor mass fraction can increase the curing rate; (2) the hydrosilylation reaction between silicones determines the curing mechanism of phosphor/silicone composite; (3) the tensile test, FE simulation and Mori–Tanaka theoretical prediction results confirm that the Young’s modulus of phosphor/silicone composite increases by gradually adding phosphors; and (4) the Young’s modulus of phosphor/silicone composite increases after the high moisture ageing test, which can be attributed to the oxidation and cross-linking reaction of silicone and the hydrolysis of phosphor powders.

Thermal and mechanical property of FCLED package component interconnected with Sn–MWCNT composite solder

Flip-chip light-emitting diode (FCLED) packages were interconnected with various contents of Sn-decorated multi-walled carbon nanotube (Sn–MWCNT) composite solder. The Sn–MWCNT was synthesized with a Sn solution using polyol to decorate Sn nanoparticle on the surface of MWCNTs. The Sn-58Bi solder pastes containing Sn–MWCNTs were printed on the metal-printed circuit boards, and then bonded with a flip-chip bonder. The mechanical property of FCLED packages with various contents of Sn–MWCNTs were evaluated with a bond tester. Thermal property was measured with IR Camera and laser flash analysis. The shear strength of an LED chip with 0.1 wt% Sn–MWCNT solder increased about 25% over that without Sn–MWCNT. The LED chip temperature with 0.1 wt% Sn–MWCNT nanocomposite solder decreased about 7% compared to that of the Sn-58Bi solder.