S. Shanmugan

Study on thermal performance of high power LED employing aluminum filled epoxy composite as thermal interface material

The demand for high power light emitting diodes (LEDs) has spawned a dramatic revolution in illumination industry. However, the miniaturization of electronic devices especially LEDs have increased the need for highly sophisticated yet cost effective thermal management solutions in order to sustain this technological advancement. This paper elucidates the thermal behaviour of an LED employing metal filled polymer matrix as thermal interface material (TIM) for an enhanced heat dissipation characteristic. Highly thermal conductive aluminium were incorporated in bisphenol A diglycidylether (DGEBA) epoxy matrix to identify the effect of filler to polymer ratio on the thermal performance of high power LEDs. The curing behaviour of DGEBA was optimized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The dispersion nature of the Al fillers into polymer matrix was verified with Field Emission Scanning Electron Microscope (FESEM). The thermal performance of synthesized Al filled polymer composite as TIM was tested with 5W green LED employing thermal transient measurement technique. Comparing the filler to polymer ratio, the rise in junction temperature for 60 % Al filled composite was higher by 11.0 °C than 50 % Al filled composite at cured state. In addition, it was also observed from the structure function analysis that the total thermal resistance was 10.96 K/W higher for 60 % Al filled composite compared to 50 % Al filled composite. On the other hand, a significant rise of 9.46 °C in the junction temperature between cured and uncured samples of 50 % Al filled polymer TIM was observed and hence the importance of curing process of metal filled polymer composite for effective heat dissipation has been discussed extensively in this work.

Performance Testing of 3-W LED Mounted on ZnO Thin Film Coated Al as Heat Sink Using Dual Interface Method

In high-power electronic devices, thermal interface material (TIM) helps to conduct heat effectively from the chip to ambient by connect the discrete points of the two mating solid surfaces. This paper demonstrates the use of zinc oxide (ZnO) thin film as TIM prepared on Al substrate using RF sputtering. The total thermal resistance (Rth-tot) measured by dual interface method is lower for ZnO coated than for bare and thermal paste applied Al substrates. The thickness of ZnO thin film also influences the thermal resistance as Rth-tot decreases with increased thickness at high driving current. Junction temperature (TJ) is also reduced noticeably for ZnO coated substrates and ATJ between bare and 800-nm ZnO thin film coated substrate is 3.33°C as high for other combinations. The thermal resistance of ZnO interface (Rth-b-hs) is also calculated from the transient curve and observed low resistance with 800-nm ZnO thin film measured at 700 mA. The observed correlated color temperature values are low for ZnO thin film coated Al substrates measured at >350 mA. ZnO thin film is supported to enhance the luminosity of the given light emitting diode and suggested for the replacement of thermal paste based interface material.

Thermal Performance of High Power LED on Boron Doped Aluminium Nitride Thin Film Coated Copper Substrates

Aims: The paper is aim to study the thermal performance of Boron doped Aluminium Nitride (B-AlN) thin film coated over Copper (Cu) substrate to improve surface configuration of the interface between two materials with different synthesis parameters. Study Design: Synthesis of Boron doped AlN thin film by sputtering and post processed for various temperatures. The processed samples were characterized to study the behavior of B doping as well as the annealing temperature in changing the properties of B doped AlN thin film. The structural and surface properties were studied and reported. Place and Duration of Study: Nano Optoelectronic Research Laboratory, School of Physics, University Sains Malaysia, Penang 11800, Malaysia, between December 2013 and July 2014. Methodology: B-AlN thin films were prepared with five different gas ratios over Cu substrates by DC-RF coupled sputtering method and suggested for thin film based thermal interface material Original Research Article Ong et al.; JSRR, 5(2): 109-119, 2015; Article no.JSRR.2015.078 110 (TIM). 3W green LED package was tested with B-AlN thin films coated Cu substrates through thermal transient and surface analysis. The results are compared with the performance of bare Cu substrates. Results: The thin film prepared with gas ratio of Ar 7: N2 13 coated at 200°C showed the lowest thermal resistance Rth (53.27 K/W), board to ambient thermal resistance RthB-A (36.03 K/W) and the lowest junction temperature Tj(120.98°C) at higher driving current (700 mA). Surface analysis results show that the thin film mentioned above exhibits low in surface roughness (8 nm) and range of valley depth (30-80 nm), which contribute in thermal performance of LED. Conclusion: Overall, B-AlN films coated with gas ratio of Ar 7: N2 13 are more favorable in reducing both total thermal resistance and junction temperature (Tj) of LED.

Heat transfer in high-power LED with thermally conductive particle-filled epoxy composite as thermal interface material for system-level analysis

This paper elucidates the thermal behaviour of an LED employing different particles filled epoxy as thermal interface material (TIM) for enhanced heat dissipation. Highly thermal conductive metal filler of aluminium (Al) and ceramic fillers of aluminium nitride (AlN) and aluminium oxide (Al2O3) were incorporated in bisphenol A diglycidylether (DGEBA) epoxy resin to identify the effect of the filler materials as TIM on the thermal performance of high power LEDs. From the thermal transient analysis of a 3W warm white LED, it was observed that the Al filled composite exhibits the lowest junction temperature of 38.3 °C compared to the other two fillers. The total thermal resistance of the package with AlN filled composite and Al2O3 filled composite were 13.77 and 15.50K/W respectively. This paper too suggests that the total thermal resistance of the LED package increases when the particle size of the fillers decrease.

Antibacterial Activity and Electrical Properties of Gold Nanoparticle Doped Ceria-Rice Husk Silica (Au/Ce-Silica) Nanocomposites Derived From Biomass

The present study deals with synthesis and characterization of gold doped in ceria-silica, derived from rice husk silica biomass materials. Large amount of silica recovered from waste rice husk silica was utilized. The silica materials derived from waste product can be used as low cost supporting material for potential applications such as catalytic oxidations and low-k dielectric material development. Gold doping on ceria-mixed silica derived from rice husk is carried out by an in situ method (Au/Ce-Silica-A) as well as by co-precipitation method (Au/Ce-Silica-B). The physicochemical characterization and antibacterial activity of as prepared material have been studied.

GROWTH OF SPUTTERED-ALUMINUM OXIDE THIN FILMS ON Si (100) AND Si (111) SUBSTRATES WITH Al2O3 BUFFER LAYER

Aluminum oxide (Al2O3) thin films with Al2O3 buffer layer were deposited on Si (100) and Si (111) substrates using RF magnetron sputtering of Al2O3 target in Ar atmosphere. The synthesized films were then annealed at the temperature of 400∘C, 600∘C and 800∘C in nitrogen (N2) environment for 6h. Structural properties and surface morphology are examined by using X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM) and Atomic Force Microscope (AFM). XRD analysis indicated that different orientation of Al2O3 were formed with different intensities due to increase in the annealing temperature. From FESEM cross-section analysis results, it is observed that the thickness of films were increased as the annealing temperature increased. EDX analysis shows that the concentration of aluminum and oxygen on both the Si substrates increased with the increase in annealing temperature. The surface roughness of the films were found to be decreased first when the annealing temperature is increased to 400∘C, yet the roughness increased when the annealing temperature is further increased to 800∘C.

Structural and Optical Properties of Chromium Doped Aluminum Nitride Thin Films Prepared by Stacking of Cr Layer on AlN Thin Film

Chromium stacked aluminum nitride (Cr-AlN) thin film was deposited on glass substrates by elemental stack method using rf sputtering. Annealing treatment was carried for about 1 hour at 100˚C, 300˚C, and 500˚C in nitrogen atmosphere for doping. Variations of the structural and optical properties of the films were studied using XRD, AFM, FESEM and UV-Vis spectroscopic technique. Structural analysis showed the presence of only (111) planes with very low intensity. From AFM and FESEM images, reduced grain size and smoothened surface morphology was achieved as the annealing temperature increases. Improved optical transmittance of Cr-AlN may be due to the diffusion of Cr into AlN as the annealing temperature increases. Decreased film thickness was also noticed for Cr-AlN thin film with annealing temperatures.

Study on thermal performance of high power LED employing aluminium filled epoxy composite as thermal interface material

The demand for high power light emitting diodes (LEDs) has spawned a dramatic revolution in illumination industry. However, the miniaturization of electronic devices especially LEDs have increased the need for highly sophisticated yet cost effective thermal management solutions in order to sustain this technological advancement. This paper elucidates the thermal behaviour of an LED employing metal filled polymer matrix as thermal interface material (TIM) for an enhanced heat dissipation characteristic. Highly thermal conductive aluminium were incorporated in bisphenol A diglycidylether (DGEBA) epoxy matrix to identify the effect of filler to polymer ratio on the thermal performance of high power LEDs. The curing behaviour of DGEBA was optimized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The dispersion nature of the Al fillers into polymer matrix was verified with Field Emission Scanning Electron Microscope (FESEM). The thermal performance of synthesized Al filled polymer composite as TIM was tested with 5W green LED employing thermal transient measurement technique. Comparing the filler to polymer ratio, the rise in junction temperature for 60 % Al filled composite was higher by 11.0 °C than 50 % Al filled composite at cured state. In addition, it was also observed from the structure function analysis that the total thermal resistance was 10.96 K/W higher for 60 % Al filled composite compared to 50 % Al filled composite. On the other hand, a significant rise of 9.46 °C in the junction temperature between cured and uncured samples of 50 % Al filled polymer TIM was observed and hence the importance of curing process of metal filled polymer composite for effective heat dissipation has been discussed extensively in this work.

Synthesis and characterisation of gold nanoparticle doped ceria-rice husk silica nanocomposites derived from biomass

To realise high performance in IC devices, it is necessary to reduce the RC delay, cross talk, and power consumption. An effective method to make these reductions is to decrease the parasitic capacitance by employing a low dielectric constant (low-k) material in the intermetal dielectrics (IMD). The present research topic deals with the synthesis and characterisation of gold doped in ceria-silica, derived from rice husk biomass materials. Large amount of silica recovered from waste rice husk silica, hence the silica materials derived from waste product can be the low cost and used for potential application such as low-k dielectric material development. Gold doping on ceria-mixed silica derived from rice husk is carried out by insitu method (Au/Ce-silica-A) and deposition-co precipitation method (Au/Ce-silica-B). Au/Ce-silica-A and Au/Ce-silica-B shown the low-k dielectric constant compared to bulk ceria-silica.

Estimation of Non-Reciprocal Behavior and Junction Temperature of an IC LED Driver by Thermal Impedance Matrix Measurement

The thermal path behaviour of the electronic device is often characterized by considering the single heat source and single junction to ambient thermal resistance. In case of IC drivers, the heat source within the device is multiple due to many integrated components such as transistor, internal resistor, and etc on the single die. Hence the evaluation of IC drivers with multiple heat sources is absolutely necessary for imparting suitable thermal management design within the devices. This study aims at evaluating the factor affecting the thermal performance of the IC driver. In this study, thermal transient measurement method and linear superposition technique have been used to measure the junction temperature of the Device under Test (DUT). Also, the thermal impedance of the DUT has been characterized using structure function extracted from the cooling curve. The obtained result of the thermal impedance showed the non-reciprocal behaviour of the thermal transfer impedance (offdiagonal). In terms of structure function, the total Rth-JA of region A is higher than region B and C. From the linear superposition technique, the junction temperature was calculated which showed that the region A (148.07 °C) showed the higher value compared to region B (132.72 °C) and C (139.46 °C). Therefore, it can be concluded that a single die has multiple heat source which increase exponentially in multiple directions resulting in invariable driver performance and failure. Thus, the presence of multiple heat source in the driver was identified as potential performance affecting factor as it caused non-uniform thermal heat distribution within the driver. The outcome of this study benefits in selection of suitable thermal management technique in IC packages.