1. Modified epoxy resin for LED packaging
Epoxy resin has high refractive index and light transmittance, and its mechanical properties and bonding properties are quite good, so some products are still used in the market.
The high temperature performance and impact resistance of epoxy resin can be improved by introducing organosilicone functional groups, and the shrinkage and thermal expansion of the epoxy resin can be reduced, and the application range of the epoxy resin can be extended.
According to the reaction mechanism, silicone modified epoxy resin can be divided into two methods: physical blending and chemical copolymerization.
If pure physical blending is relied on, due to the large difference in solubility coefficient between silicone and epoxy resin, the microscopic phase structure is easy to be separated, and the modification effect is not good. Therefore, it is generally necessary to improve its compatibility performance by adding transition compatibility groups.
S. S. Hou et al. used hydrogen-containing polysiloxane and allyl glycidyl ether for hydrogen-siloxane addition reaction to prepare polysiloxane containing epoxy group, and then blended it with bisphenol A type epoxy resin.
The experimental results show that the microphase structure of the modified product is good and there is no phase separation.
The chemical copolymerization method is to use the active groups on the organosilicone polymer, such as hydroxyl group, alkoxy group, etc., to react with the active groups on the epoxy resin, such as the epoxy group, to generate the copolymer to achieve the purpose of modification.
As early as 2007, some people abroad used this method to study the application of silicone copolymerization modified epoxy packaging material in LED products. The experiment proved that this method could significantly improve the impact resistance and high and low temperature resistance of the packaging material, and significantly reduce the shrinkage rate and thermal expansion coefficient.