Preparation And Characterization Of Nano-SiO₂/EP Coating Used On Thin Film Resistors

Epoxy resins (EP) have been widely used in electronics encapsulation fields for their outstanding advantages on adhesive, modulus and techniques. However, heat-resistant, wet-resistant and mechanical properties of EP were not fit for protection and loadsupporting electronic device, modification of EP has been very active.Nano-particles were used to prepare high performance resins by filling modification for their large specific surface and high surfacial activity. Modification of EP by nano-SiO2 and organic silicone was presented to enhance heat-resistant, wet-resistant and mechanical properties of EP cured system by review of nano-composites, modification of EP and nano-SiO2.Polymerization of epoxy resin and TEOS with dispersing nano-SiO2 was studied. By IR, TG and SEM analyses, high temperature performance of composites was improved obviously by forming Si－O－Si net structure with increasing contents of TEOS and forming lots of tie points with increasing contents of nano-SiO2, wet-resistant of modified EP was mainly influenced by contents of Si－OH and alkyl, toughness of modified EP was improved by adding nano-SiO2.EP cured by anhydride was modified by nano-SiO2 and TEOS, heat-resistant of modified EP was improved obviously as increasing integrity of Si－O－Si net by adding nano-SiO2 and TEOS. A uniform design was performed with four factors: quality of nano-SiO2, volume of tetraethyl orthosilicate, quality of maleic anhydride and volume of triethanolanine, thermostability and electrical insulation of the resins were determined as responses. Analyses of response surfaces showed that Td and T0.8 can be increased as the increase of mSiO2 and mMA?VTEA, and can be decreased as the increase of VTEOS and mMA2, m% and ρv can be decreased as the increase of mSiO2 and mMA?VTEA, and can be increased as the increase of VTEOS and mMA2. The effects of mSiO2 and mMA2 on responses were remarkable in the experimental domain examined. Td was linearity increased as the increase of mSiO2 and conic decreased as the increase of mMA, T0.8 was linearity increased as the increase of mSiO2 and conic decreased as the increase of mMA, m% was linearity decreased as the increase of mSiO2 and conic increased as the increase of mMA, ρv was linearity decreased as the increase of mSiO2 and conic increased as the increase of mMA. Polymer of EP and organic silicone was modified by nano-SiO2 covering with coupling agent. For nano-SiO2/EP and common SiO2/EP, maximum value of thermal decomposition temperature, impact strength and volume resistivity were 323℃, 89.2kJ.m-2 and 3.56×1014Ω.cm; 308℃, 17.13kJ.m-2 and 2.80×1014Ω.cm respectively, as contents of nano-SiO2 and common SiO2 were both 4%. Toughness of EP was enhanced with adding SiO2 particles; enhancing effect of nano-SiO2 was better than common SiO2.Effects of mSiO2, Vorganosilicon, Vcure, Vcoupling agent, Vsolvent, mE－20 and Tcured on heat-resistant and insulating properties of nano-SiO2/organic silicone/EP composites were studied by uniform design. Analyses of response surfaces showed that Td, T0.8, m% and logρv were influenced obviously by Vcoupling agent, mSiO2.Vorganosilicon, mSiO2.Vcure and Vcure.Vcoupling agent. When other factors were mean quantities, Td, T0.8, m% and logρv can be decreased scalariformly as the increase of Vcoupling agent and Vcure; can be increased as the increase of mSiO2, Vsolvent and Tcured; Td, T0.8 and m% can be increased as the increase of Vorganosilicon and mE－20; logρv can be decreased as the increase of Vorganosilicon and mE－20. ΔR/R of thin film resistors coated with coating obtained under optimizing conditions were 0.5% and 0.25% respectively after water boiling and overburden test.