U.S. engineers have developed a new type of thermal interface material for LED cooling

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Polymeric materials are usually for thermal insulator, but U.S. researchers make the polymer fibers arranged in neat array by electro-polymerization, forming a new type of thermal interface material, thermal performance improved 20-fold based on the original. The new material can be reliable operation at a temperature up to 200 ℃. It can be used for cooling high-brightness LED, automobiles, electronic equipment and internet server. The research achievement is published in "Nature Nanotechnology" magazine online edition.

As electronic devices became more powerful, smaller size, thermal issues are becoming increasingly complex. Engineers have been looking for better thermal interface materials, to help electronic devices dissipate heat effectively. The amorphous polymer material is a poor conductor of heat, since their disorder limit the heat conduction phonon transfer.

Assistant Professor, Georgia Institute of Technology, George Woodruff School of Mechanical Engineering Balatude carat says, new thermal interface material made ​​of conjugated polymers, which is not only neat nanofiber arrays conducive phonon transition, but also to avoid brittle material.

The thermal conductivity of new material will at room temperature of 4.4 watts / meter Kelvin. And has been conducted 80 times heat cycle test at a temperature of 200 ℃, the performance remains stable.

Nanofiber array structure is manufactured by a plurality of steps. Researchers first monomer containing an electrolyte is coated on a template with minute pores of the alumina, and then applying an electrical potential to the template, each of the apertures in the electrodes will attract the monomers, the formation of the hollow nanofiber.

The length and thickness of the fibers are control by the amount of current and time. the size of the pores ranging from 18 nm to 300 nm determines by the diameter of the fiber. Traditional thermal interface material thickness of about 50 microns to 75 microns and the thickness of the new material obtained in this manner can be as thin as 3 microns.

Carat said the technology still needs further improvement, but he believes it will be able to expand production and commercialization.

LED Color Mixture Principle

The High-brightness (HB) LED which have more advantages than traditional lighting solutions is become increasingly popular. One of the advantages of high brightness LED is its ability to produce different colors. The essence of the color mixture is to mixing the base primary color in appropriate proportions to generate the secondary color. This article will explain the science behind color mixing, including those involving mathematical formulas and how to apply them effectively.

Color mixture and multi-point excitation space principle

The basic properties of light are not primary colors, but often involve psychological reaction when the eyes receive light. Color model can be expressed in different ways. Modeling goal is to minimize the complexity of the formulas and the number of variables, while maximizing the essence and coverage. Traditionally, no matter what the meaning assigned to the variable, which is sufficient to describe all three colors: RGB, Hue - Saturation - Brightness (HSB). Other based on shades - saturation model, as Lab and XYZ. Their common feature is a variable quantity or dimension.

In the multi-point excitation space, color excitation is mark by letter R, Q, G, B, and A. Q refers to excitation of any color, the letter R, G, B and A, are expressed the selected basic fixed excitation for color blending. Red, green, blue and amber are fundamental excitation. Color matching means for a given excitation Q determined by a variety of basic excitation R, G, B and A with appropriate quantities obtained additional mixture color which is available expressed as vector equation.

Q=RqR+GqG+BqB+……+AqA (equation (1))

In the multi-dimensional space, color excitation Q is expressed by multiple-support excitation vector Q. Scalar multiplier RQ, GQ, BQ and AQ are excited by a given basic excitation R, G, B and A which are in units of measure by convention. Unit vectors R, G, B, and A represents a fundamental excitation, which define the space. They have a common starting point to four different directions.

Figure 1: multi-dimensional color space

The origin of vector Q is the same as R, G, B and A. It located by the R, G, B and A defined axes, lengths equal to Q multi-stimulus values ​​RQ, GQ, BQ and AQ. We can obtain the direction and length by a defined formula equation (1). The space which defined by R, G, B and A is called a multi-excitation.

Color Mixture

Figure 2 shows the CIE 1932 chromaticity diagram. There are three colors in the figure 2: Red, Green, Blue. Through three colors mixed in appropriate proportions, we can get all the colors on the connection. This area is called the color gamut. However, in the CIE 1931 standard, the color distribution is uneven and discontinuous. For calculated ratio of primary color in determining to form the desired secondary color, the linear transformation can’t be used.

Blending algorithm

In mixing colors applications, the firmware in accordance with CIE chromaticity coordinates input values. For each LED channel, it converted coordinate into values ​​of the appropriate dimming. In laymen's terms, dimming value is the LED dimming range that must have the corresponding maximum flux. If intelligently and quickly turned off the LED bulb current, can be implemented to control the LED luminous flux output. The firmware will let the coordinate combines with LED knowledge in the pre-programmed system. Then, it will be necessary to finish the chromaticity coordinates correctly converted into a luminance value of each LED.

LED downlight-Application of Thermal Plastic in LED Downlight / Bulb-Article-Future

LED downlight-Application of Thermal Plastic in LED Downlight / Bulb-Article-Future

More conventional thermally conductive material is a metal and metal oxide, and other non-metallic materials, such as graphite, carbon black, A1N, SiC. With the development of science and technology and the production of many products on the thermal conductivity material put forward higher requirements, want to have more excellent performance, light weight, resistance to chemical corrosion resistance, excellent electrical insulating properties, impact resistance, easy molding, etc. . Thermal insulating polymer composites because of their excellent performance more and more widely used.

However, due to polymer materials, mostly poor conductor of heat, limiting its application in terms of thermal conductivity, and thus the development of new polymer materials with good thermal conductivity, thermal conductivity now become an important development direction of the material. Especially in recent years, with the rapid development of high-power electronics, electrical products, is bound to be more and more problems due to product heat, resulting in lower product efficacy, shorten the service life. Some data indicate that electronic components temperature is increased by 2 ℃, which fell 10 percent reliability; life expectancy is only 25 ℃ 50 ℃ at the time of 1/6.

Thermally conductive filler is mainly divided into two types: one is the thermal insulation filler, such as metal oxides, metal nitrides. The other is a non-thermal insulation fillers, such as carbon-based and various metal. The former is mainly used in electronic components such as packaging materials for electrical insulation performance requirements of the occasion, the latter is mainly used for heat exchangers and other chemical equipment electrical insulation performance requirements for lower occasions.

Currently domestic power LED lamps(LED bulb) commonly used in aluminum industry as a shell cooling materials, the use of thermal plastic housing can save a lot of energy and improve production efficiency, reducing the cost of LED products have a very real economic significance. Can greatly expand the use of plastic lighting engineers to develop products and creative spirit and design more portable, beautiful products for faster promotion to consumers. We propose on the basis of extensive research on the use of thermal plastic production 8 watt and 10-watt LED downlight base through the mold, temperature check whether all parts of the product comply with the requirements to test thermal plastic is qualified for mass production.

Use substrate microfabrication double LED brightness

Japanese prince holdings announced, they have established the particles precision coating technology also microfabrication technology, and successfully make the doubled brightness of the LED and the organic EL element. The company indicated, sapphire substrate use for LED after process of this technology will on market in 2016. They show the organic EL element and LED on LED Next Stage 2014 in Tokyo Japan.

Recently, many high-efficiency LED is processed using a surface fine concavo-convex sapphire substrate or wavy "PSS (Patterned Sapphire Substrate)". There are a large number of cases indicate that with the PSS that the gallium nitride (GaN) crystal on the substrate more easily reflect light, can improve the light extraction efficiency of the LED, the light emitting efficiency can be increased from 20 to 30%.

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