Application of new materials in thermal management of LED industry

"12th Five-Year" seven strategic emerging industry development plan and the introduction of local energy saving and environmental protection LED lighting promotion policies, LED lighting brings significant development opportunities. According to industry reports, China's LED lighting industry market size from 2008 to 2012 from less than 14 billion to about 80 billion growth, the growth rate of about 484%, is expected in 2013 China's LED lighting industry will exceed 100 billion, a growth rate of 38.6%.

In the LED industry chain, the upstream chip, epitaxy and other key technologies are international manufacturers (PhilipsLumileds, CK, CREE, Nichia, OSRAM, etc.) firmly control. The domestic LED market competition is mainly concentrated in the middle and downstream processing terminal and part of the low value of supporting industries, and regions of Pearl River Delta, Yangtze River Delta, northern area, Min River Delta region four industrial chain formation in the region.

Figure 1:LED industry chain and representative company

With the popularization and development of high-power LED lighting, the requirement of product components on the heat dissipation performance is higher and higher. Efficient thermal management has become the key to the development of high power LED. At present, the efficient energy conversion and thermal energy control in the LED industry are mainly realized through three aspects: chip, package and system integration, which mainly include structural improvement and new material application in two ways.

The improvement of structure is to realize the thermal management by increasing the radiating area and improving the convection radiation. The technology is relatively difficult, easy to implement, can be widely used in production. Today, the LED industry, the main cooling technology are: micro channel complex disguised technology, heat pipe technology, spray cooling technology, thermoelectric refrigeration, thermoacoustic refrigeration technology, the synthetic jet and vibration refrigeration technology, vapor compression refrigeration technology etc.. However, this method affects the product volume, cost, quality and packaging density, and can not increase the heat dissipation area.

The application of new materials is the focus of the current LED thermal management, through the use of high thermal conductivity material directly improve the performance of components. The transition to LED lighting lighting industry in the traditional lighting, the thermal conductivity of materials has experienced the first generation and the two generation to the four generation, third conversion of advanced materials, traditional materials gradually to diamond series composite materials, carbon materials, thermal interface materials as the representative of the new material to replace. More and more new materials are used in LED substrates and packages.

As far as the LED industry is concerned, the application of new materials on the substrate and package is of great significance to the realization of LED high efficiency thermal management. In this paper, we focus on the new thermal conductive materials used in the LED industry and their properties, such as diamond series composites, silicon carbide aluminum, carbon materials and other materials.

Diamond composite material

Diamond composite materials are mainly diamond / copper, diamond / aluminum. The diamond series composites with copper / aluminum as the matrix and diamond particles as functional components have the advantages of high thermal conductivity, low thermal expansion coefficient, low density, good plating and processability. The main preparation methods are: high temperature and high pressure, spark plasma sintering, powder metallurgy (cold pressing sintering, hot pressing method), liquid phase infiltration method and so on. The main factors affecting the production of diamond and the wettability of copper / aluminum, the graphitization of diamond and the manufacturing cost are the main problems. The production enterprises and domestic less, such as the Beijing General Research Institute of nonferrous metals (GRINM), climbing China, bench drill technology etc..

The development of Beijing Nonferrous Metal Research Institute of the fourth generation of high thermal conductivity, low thermal expansion of diamond / copper thermal conductivity of 650 W/m above K, the thermal expansion coefficient of 5-7 * 10-6/ DEG C, and quite similar foreign products, the leading domestic, in high power semiconductor lighting devices and other parts should be used to study the heat sink. Diamond / copper composite materials in the application of heat dissipation of high power LED devices significantly, junction temperature is reduced by 10.6%, a 33.3% reduction in thermal resistance of high power LED device lifetime and reliability greatly improved, give full play to the advantages of the material.

Two aluminum silicon carbide

SiC / Al is a kind of particle reinforced metal matrix composites with aluminum alloy as matrix and SiC particles as reinforcements. Because of its high thermal conductivity, thermal expansion coefficient, small density, light weight, high hardness and high bending strength, it is used in LED electronic packaging. Silicon carbide / aluminum is widely used in the substrate, there are a number of companies such as General Research Institute, Jiangsu Ding Kai (agent TTC materials) and other production. The new aluminum silicon carbide composite material of Beijing Nonferrous Metal Research Institute has the feature of "light, hard, just, clever, cheap and beautiful", to meet the lightweight and high density packaging requirements, and is suitable for wide application of LED, aviation, aerospace, electronic components, such as shell package.

Table 1: the performance parameters of LED thermal conductivity materials of Beijing Nonferrous Metals Research Institute

Three carbon materials

Carbon materials are mainly made of graphite, graphite film and so on, which is characterized by the conductivity of the metal material, the plasticity of the organic plastic, the high plane thermal performance, the chemical stability and so on. In addition to the high thermal conductivity of similar metal materials, thin, flexible, the performance of its widely used in electronic machines, semiconductors, lithium batteries, such as heat sinks and radiator parts. Once published, carbon materials quickly in LED electronics, tablet PCs, handheld devices, especially in smart phones widely used. The main suppliers of the domestic market are South Korea SKC, Shenzhen base stone, across the limited company, etc..