(Jiangxi New Materials Co., Ltd.)

OFweekSemiconductor LightingNet NewsLED (Light Emitting Diode) has the characteristics of energy saving and environmental protection, long life, low voltage and short switching time. Short and other characteristics, it is widely used in lighting, display, backlight and many other fields. It is currently developing in the direction of higher brightness, high color, high weather resistance, and high luminous uniformity. The LED industry chain can be divided into upstream, midstream and downstream, which are LED epitaxial chips, LED packaging and LED applications. As the link between the previous and the next in the LED industry chain, LED packaging plays an important role in the entire industry chain. LEDs are composed of chips, wires, brackets, conductive glue, packaging materials, etc. Among them, packaging materials are one of the key factors that affect the performance and service life of LEDs. At present, due to their special requirements for light transmittance, packaging materials currently used on the market mainly include high-transparency materials such as epoxy resin, silicone, polycarbonate, glass, and polymethacrylate. However, since most of these materials are hard and inconvenient to process, they are basically used as outer lens materials. Traditional LED epoxy resin packaging materials have defects such as large internal stress, poor heat resistance, and easy aging. They cannot meet the growing needs for LED packaging material performance and are gradually being replaced by silicone materials or silicone modified materials. Silicone material is a material with high UV resistance, high aging resistance and low stress, making it an ideal choice for LED packaging materials. The light transmittance of silicone resin is directly proportional to the luminous intensity and efficiency of the LED device. The higher the light transmittance, the better the luminous intensity and efficiency of the LED device. Since gallium nitride chips have a high refractive index (about 2.2), the refractive index of general organic silicon materials is only 1.4. Therefore, increasing the refractive index of organic silicon materials can reduce the difference in refractive index with the chip, and reduce interface reflection and refractive bands. This reduces the light loss and enhances the light extraction efficiency of the LED device.

1. Modified epoxy resin for LED packaging

(Jiangxi New Materials Co., Ltd.)

Epoxy resin has a high refractive index and light transmittance, and its mechanical properties and bonding properties are quite good, so there are still certain products in the market. By introducing silicone functional groups to modify epoxy resin, the high-temperature performance and impact resistance of epoxy resin can be improved, the shrinkage rate and thermal expansion of the product can be reduced, and the application range of the product can be improved. According to the reaction mechanism, silicone-modified epoxy resin can be divided into two methods: physical blending and chemical copolymerization. If you rely purely on physical blending, since the solubility coefficients of silicone and epoxy resin are quite different, the microphase structure is easily separated and the modification effect is not good. Generally, it needs to be improved by adding transition compatible groups. its compatibility properties. S. S. Hou et al. used hydrogen-containing polysiloxane and allyl glycidyl ether to perform a hydrosilylation reaction to prepare polysiloxane containing epoxy groups, and then blended it with bisphenol A-type epoxy resin. The experimental results show that the modified product has a better microscopic phase structure and no phase separation.

The chemical copolymerization method uses reactive groups on the silicone polymer, such as hydroxyl groups, alkoxy groups, etc., to react with reactive groups such as epoxy groups on the epoxy resin to generate a copolymer for the purpose of modification. As early as 2007, someone abroad used this method to carry out research on using silicone copolymer modified epoxy packaging materials for LED products. Experiments proved that this method can significantly improve the impact resistance and high and low temperature resistance of the packaging materials. Improvement, shrinkage and thermal expansion coefficient are significantly reduced. Deborah et al. used a condensation reaction to mix 4-vinyl oxirane with various silanes such as bis(dimethylsilane)tetraphenylcyclotetrasiloxane and tris(dimethylsilane)phenylsiloxane. After the reaction, a modified epoxy resin product with excellent impact resistance, strong UV aging resistance, high light transmittance, and thermal expansion coefficient that meets the requirements of chip products is produced. Li Xueming et al. used UV curing technology to cross-link and hybridize polyorganosilsesquioxane and epoxy resin in situ to obtain a product with high light transmittance, strong thermal stability, UV aging resistance, excellent impact resistance and high adhesion. The epoxy polyorganosilsesquioxane hybrid film material can be used to replace the currently used high-temperature curing epoxy materials and is used in LED, electronic packaging and other industries. Seung Cheol Yang et al. used alicyclic epoxy resin to react with diphenyldihydroxy and triphenylhydroxyl to obtain a silicone epoxy modified material with high refractive index (1.58), good thermal stability and UV resistance. Huang Yunxin et al. first synthesized oligomeric silsesquioxanes of different molecular weights, and used the synthesized polyorganosiloxanes to modify bisphenol A-type epoxy resins. The results showed that all three polysiloxanes could improve the performance of epoxy resins. Product toughness and flexural strength. Yang Xin et al. prepared multifunctional silicone epoxy resin through the hydrolysis and condensation reaction of 2-(3,4-epoxycyclohexyl)ethylmethyldiethoxysilane, using methylhexahydrophthalic anhydride as the curing agent , the obtained product has greatly improved light transmittance and heat aging resistance, and is expected to be popularized and applied in the field of LED packaging materials. Crivello. J et al. used epoxy monomers containing double bonds including allyl glycidyl ether and 4-vinyl epoxycyclohexane, and hydrogen-containing polysiloxane.Carry out hydrosilation reaction to synthesize silicone-modified epoxy resin, which has good transparency and heat resistance.