High Current Injection to a UV-LED grown on a Bulk AlN Substrate

2003 ◽  
Vol 798 ◽  
Author(s):  
Toshio Nishida ◽  
Tomoyuki Ban ◽  
Hisao Saito ◽  
Toshiki Makimoto
Keyword(s):  
Thermal Conductivity ◽  
Heat Dissipation ◽  
Light Emitting Diode ◽  
Peak Shift ◽  
Emission Peak ◽  
Injection Current ◽  
High Thermal Conductivity ◽  
Uv Led ◽  
High Injection ◽  
Large Injection

ABSTRACTWe applied a bulk AlN substrate to an AlGaN-based ultraviolet light emitting diode (UV-LED) and found that this combination enables high injection current, which shows the LED's potential for large ultraviolet flux extraction. Heat dissipation is an important issue for LEDs. Bulk AlN substrate has high thermal conductivity, a wurtzite crystal symmetry the same as that of nitride emitters, and transparency in the ultraviolet wavelength range. An UV-LED grown on a bulk AlN substrate shows output power linearity up to high injection current up to 300 mA, whereas a similar device grown on an AlN-template formed on a sapphire substrate only shows linearity up to an injection current of about 150 mA. It also showed very stable emission peak wavelength. For example, the emission peak shift is less than 2 nm in spite of the large injection current of 200 mA. Both findings are attributed to the heat dissipation afforded by the high thermal conductivity of the bulk AlN. This LED still suffers from internal absorption loss caused by the residual color centers in the AlN at present. However, further improvement of bulk AlN substrates will lead to high flux and highly efficient ultraviolet sources.

scholarly journals Development of Thermally Conductive Polyurethane Composite by Low Filler Loading of Spherical BN/PMMA Composite Powder

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Kai-Han Su ◽  
Cherng-Yuh Su ◽  
Cheng-Ta Cho ◽  
Chung-Hsuan Lin ◽  
Guan-Fu Jhou ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Dissipation ◽  
Three Dimensional ◽  
Filler Loading ◽  
High Thermal Conductivity ◽  
Heat Diffusion ◽  
Composite Powders ◽  
Polyurethane Composite ◽  
Uniform Dispersion ◽  
Thermally Conductive

Abstract The issue of electronic heat dissipation has received much attention in recent times and has become one of the key factors in electronic components such as circuit boards. Therefore, designing of materials with good thermal conductivity is vital. In this work, a thermally conductive SBP/PU composite was prepared wherein the spherical h-BN@PMMA (SBP) composite powders were dispersed in the polyurethane (PU) matrix. The thermal conductivity of SBP was found to be significantly higher than that of the pure h-BN/PU composite at the same h-BN filler loading. The SBP/PU composite can reach a high thermal conductivity of 7.3 Wm−1 K−1 which is twice as high as that of pure h-BN/PU composite without surface treatment in the same condition. This enhancement in the property can be attributed to the uniform dispersion of SBP in the PU polymer matrix that leads to a three-dimensional continuous heat conduction thereby improving the heat diffusion of the entire composite. Hence, we provide a valuable method for preparing a 3-dimensional heat flow path in polyurethane composite, leading to a high thermal conductivity with a small amount of filler.

Enhanced thermal conductivity and flame retardancy of polyamide 6/flame retardant composites with hexagonal boron nitride

2018 ◽  
Vol 38 (8) ◽  
pp. 767-774 ◽  
Author(s):  
Liang Wang ◽  
Luchong Zhang ◽  
Andreas Fischer ◽  
Yuhua Zhong ◽  
Dietmar Drummer ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Boron Nitride ◽  
Flame Retardant ◽  
Flame Retardancy ◽  
High Performance ◽  
Heat Dissipation ◽  
Hexagonal Boron Nitride ◽  
Light Emitting Diode ◽  
Polyamide 6 ◽  
Twin Screw

Abstract High performance composite of polyamide 6 (PA6)/flame retardant (FR)/hexagonal boron nitride (hBN) was prepared via twin screw extrusion, followed by injection molding. The heat dissipation of the composite was significantly improved by incorporating 40 vol% of hBN, and the corresponding thermal conductivity was up to 5.701 W/(m·K), nearly 17 times that of the PA6/FR composites. In addition, the combination effect of hBN and FR to the flame retardancy of the composites was observed, and the addition of hBN could dramatically enhance the flame retardancy of composites, achieving a UL94 V-0 rating with a limited oxygen index (LOI) value of 37%. This multifunctional modification would broaden the application field of PA6 composites in light-emitting diode (LED) lamps, electronic products, and so on.

scholarly journals High thermal conductivity in soft elastomers with elongated liquid metal inclusions

2017 ◽  
Vol 114 (9) ◽  
pp. 2143-2148 ◽  
Author(s):  
Michael D. Bartlett ◽  
Navid Kazem ◽  
Matthew J. Powell-Palm ◽  
Xiaonan Huang ◽  
Wenhuan Sun ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Liquid Metal ◽  
Heat Dissipation ◽  
Dielectric Materials ◽  
Phonon Transport ◽  
High Thermal Conductivity ◽  
Stretchable Electronics ◽  
Mechanical Stiffness ◽  
Mechanical Coupling ◽  
Thermally Conductive

Soft dielectric materials typically exhibit poor heat transfer properties due to the dynamics of phonon transport, which constrain thermal conductivity (k) to decrease monotonically with decreasing elastic modulus (E). This thermal−mechanical trade-off is limiting for wearable computing, soft robotics, and other emerging applications that require materials with both high thermal conductivity and low mechanical stiffness. Here, we overcome this constraint with an electrically insulating composite that exhibits an unprecedented combination of metal-like thermal conductivity, an elastic compliance similar to soft biological tissue (Young’s modulus < 100 kPa), and the capability to undergo extreme deformations (>600% strain). By incorporating liquid metal (LM) microdroplets into a soft elastomer, we achieve a ∼25× increase in thermal conductivity (4.7 ± 0.2 W⋅m−1⋅K−1) over the base polymer (0.20 ± 0.01 W⋅m−1·K−1) under stress-free conditions and a ∼50× increase (9.8 ± 0.8 W⋅m−1·K−1) when strained. This exceptional combination of thermal and mechanical properties is enabled by a unique thermal−mechanical coupling that exploits the deformability of the LM inclusions to create thermally conductive pathways in situ. Moreover, these materials offer possibilities for passive heat exchange in stretchable electronics and bioinspired robotics, which we demonstrate through the rapid heat dissipation of an elastomer-mounted extreme high-power LED lamp and a swimming soft robot.

scholarly journals Preparation, Properties and Mechanisms of Carbon Fiber/Polymer Composites for Thermal Management Applications

Polymers ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 169
Author(s):  
Zulfiqar Ali ◽  
Yuan Gao ◽  
Bo Tang ◽  
Xinfeng Wu ◽  
Ying Wang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Carbon Fiber ◽  
Polymer Composites ◽  
Thermal Management ◽  
Heat Dissipation ◽  
Light Emitting Diode ◽  
Circuit Board ◽  
Research Progress ◽  
Good Mechanical Property ◽  
Preparation Methods

With the increasing integration and miniaturization of electronic devices, heat dissipation has become a major challenge. The traditional printed polymer circuit board can no longer meet the heat dissipation demands of microelectronic equipment. If the heat cannot be removed quickly and effectively, the efficiency of the devices will be decreased and their lifetime will be shortened. In addition, the development of the aerospace, automobiles, light emitting diode (LED{ TA \1 “LED; lightemitting diode” \s “LED” \c 1 }) and energy harvesting and conversion has gradually increased the demand for low-density and high thermal conductive materials. In recent years, carbon fiber (CF{ TA \1 “CF; carbon fiber” \c 1 }) has been widely used for the preparation of polymer composites due to its good mechanical property and ultra-high thermal conductivity. CF materials easily form thermal conduction paths through polymer composites to improve the thermal conductivity. This paper describes the research progress, thermal conductivity mechanisms, preparation methods, factors influencing thermal conductivity and provides relevant suggestions for the development of CF composites for thermal management.

High thermal conductivity liquid metal pad for heat dissipation in electronic devices

2018 ◽  
Vol 124 (5) ◽  
Author(s):  
Zuoye Lin ◽  
Huiqiang Liu ◽  
Qiuguo Li ◽  
Han Liu ◽  
Sheng Chu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Liquid Metal ◽  
Heat Dissipation ◽  
Electronic Devices ◽  
High Thermal Conductivity

scholarly journals Enhancement of thermal conductivity in polyamide-6/graphene composites via a “bridge effect” of silicon carbide whiskers

RSC Advances ◽  
2017 ◽  
Vol 7 (73) ◽  
pp. 46306-46312 ◽  
Author(s):  
Na Song ◽  
Haidong Pan ◽  
Xingshuang Hou ◽  
Siqi Cui ◽  
Liyi Shi ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Silicon Carbide ◽  
Polymer Composite ◽  
Heat Dissipation ◽  
Electronic Devices ◽  
Polyamide 6 ◽  
High Thermal Conductivity ◽  
Silicon Carbide Whiskers ◽  
Plane Direction

It is urgent to manufacture a polymer composite that has high thermal conductivity (especially in the through-plane direction) and mechanical properties simultaneously to meet the heat dissipation requirement of electronic devices.

scholarly journals Graphene−Perfluoroalkoxy Nanocomposite with High Through-Plane Thermal Conductivity Fabricated by Hot-Pressing

Nanomaterials ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 1320 ◽  
Author(s):  
Xinru Zhang ◽  
Xiaoyu Xie ◽  
Xinzhi Cai ◽  
Zeyi Jiang ◽  
Ting Gao ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Hot Pressing ◽  
Large Scale ◽  
Heat Dissipation ◽  
Graphene Nanosheets ◽  
Light Emitting Diode ◽  
Rapid Development ◽  
Portable Devices ◽  
Scale Production ◽  
Vertically Aligned

With the rapid development of electronics and portable devices, polymer nanocomposites with high through-plane thermal conductivity (TC) are urgently needed. In this work, we fabricated graphene nanosheets−perfluoroalkoxy (GNs−PFA) composite sheets with high through-plane TCs via hot-pressing followed by mechanical machining. When the GNs content exceeded 10 wt%, GNs were vertically aligned in the PFA matrix, and the through-plane TCs of nanocomposites were 10–15 times higher than their in-plane TCs. In particular, the composite with 30 wt% GNs exhibited a through-plane TC of 25.57 W/(m·K), which was 9700% higher than that of pure PFA. The composite with 30 wt% GNs was attached to the surface of a high-power light-emitting diode (LED) to assess its heat-dissipation capability. The composite with vertically aligned GNs lowered the LED surface temperature by approximately 16 °C compared with pure PFA. Our facile, low-cost method allows for the large-scale production of GNs–PFA nanocomposites with high through-plane TCs, which can be used in various thermal-management applications.

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