Wuhan Ji electronic materials experts said silicone rubber LED energy saving key

In the global energy shortage, environmental concerns in twenty-first Century, led with its high efficiency and energy saving and environmental protection, in the field of lighting has been an unprecedented opportunity. LED Diode (Light Emitting, abbreviated as LED) is a kind of semiconductor light emitting device which can convert electric energy into light energy. Compared with the traditional incandescent lamp, LED light source has many advantages, such as high brightness, long life, energy saving, no pollution, flexibility, impact resistance and so on. The study said that if the United States 55% of incandescent and fluorescent lamps are replaced by LED, the annual savings of $35 billion electricity bill and reduce the amount of carbon dioxide emissions by 7.55 tons. Japan's 100% incandescent light for LED, can reduce the amount of nuclear power plants from 1 to 2, annual savings of more than 1 billion liters of crude oil consumption. LED lamp with a significant advantage, will lead to the history of human lighting following the incandescent lamp, fluorescent lamp after the new lighting revolution.

In recent years, with the rapid development of the LED chip technology and the maturity of the driving circuit, the high power white LED has not only become the darling of architectural lighting, but also more and more to the home lighting. However, there are some problems in LED packaging technology, which restrict the further development of LED in the field of lighting. It can not reflect the advantages of high brightness, long life and energy saving. The basic task of the package is to protect the LED chip from the external environment, the external lead is connected to the electrode of the LED chip, and the luminous efficiency is improved. The main difficulty of packaging technology is that the packaging material is poor in heat dissipation and poor light emission. The temperature of the packaging material comes from the heat released by the heat generated by the LED chip, and the key to improve the luminous efficiency lies in the selection and application of the packaging material and phosphor. Due to the good thermal stability and optical properties of silicone rubber, the major LED manufacturers in the world are mainly using two component transparent silicone rubber as packaging material. However, the thermal stability of silicone rubber is good, but the thermal conductivity is poor, LED after a period of time, most of the heat accumulated in silicone rubber material is difficult to distribute, resulting in rapid aging of materials. So far, many reports on the failure of LED lighting products are related to the aging of silicone rubber materials. It is because of the aging mechanism of silicon rubber, the relationship between molecular structure and optical characteristics of the understanding is not thorough, the major international LED lighting company is not in their products to accurately predict the lifetime of LED, delay the LED product truly universal use.

Recently, electronic materials expert Dr. Cai Dengke (Dortmund Polytechnic University) in the International Journal of molecular spectroscopy "famous structure" (Journal of Molecular Structure) published a detailed introduction and analysis of the physicochemical characteristics of the silicone rubber "Raman, infrared, near infrared and ultraviolet visible spectra of silicon rubber polymer waveguide materials the characterization of" "Raman, mid-infrared, near-infrared and ultraviolet spectroscopy of PDMS silicone - visible rubber for characterization of polymer optical waveguide materials". Cai found that the molecular vibration of C-H is the main reason for the absorption of silicone rubber in some visible light. He elaborated from the ultraviolet to the optical molecular structure and infrared absorption spectrum between the silicon rubber, define the range of visible light absorption spectra of silicon rubber, analysis and summary of the visible range of the absorption peak and absorption intensity accurately. Because the present organic aging analysis is widely used in spectroscopy analysis method, so researchers can according to spectral data drawn by Dr. Cai, from the molecular structure to accurately determine the cause of the failure of the silicone rubber, silicone rubber material and feedback to the company or LED research institutions, to improve the reliability of material and Application in LED products the corresponding molecular silicone rubber. In this paper, the data and analysis results will play an important role in the solution of the aging problem of LED products.

Another problem of silicone rubber used as LED packaging material is that, due to the significant difference in mechanical properties of silicone rubber and LED chips, the internal high temperature will cause it to peel off from the LED chip and ultimately affect the luminous efficiency. Dr. CAI in the international famous magazine "microfluidic microfluidic and nanofluidic" (Microfluidic and Nanofluidic) published the paper "for the silicone rubber substrate composed of various microfluidic devices cost control and reliable adhesion method" "Cost-effective and rELiable sealing method for PDMS (PolyDiMethylSiloxane) based microfluidic devices with various substrates" this paper proposes solutions. Through the study of the polymerization of silicone rubber, it was found that the addition of molecules had a significant effect on the polymerization of silicone rubber. At the same time, through mechanical testing and electronic industry standard aging test confirmed that Dr. Cai summarized and developed a siloxane based material, adhesive agent can be widely used in a variety of substrates is resistant to high temperature, acid, alkali and other harsh conditions. The adhesive can be adhered on a variety of substrates by simple spraying or spin coating, and the thickness of 10 to 20 nm can ensure that the silicone rubber and the chip substrate form a firm chemical adhesion. Since the adhesive itself is also a silicone material, it will not affect the optical properties of silicone rubber, so it is very suitable for LED packaging.

In the middle and lower reaches of the LED industry chain, packaging is an important link between the industry and the market. LED packaging is related to the fields of light, heat, electricity, polymer materials and so on