Toughening of epoxy resins by modification with dispersed acrylate rubber for electronic packaging

Dispersed acrylate rubbers were used to improve the toughness of cresol‐formaldehyde Novolac epoxy resin cured with phenolic novolac resin for electronic encapsulation application. The effect of the alkyl group of the acrylate monomer on the phase separation of resultant elastomers from epoxy resin was investigated. The dispersed acrylate rubbers effectively improve the toughness of cured epoxy resins by reducing the coefficient of thermal expansion (CTE) and flexural modulus, while the glass transition temperature ( T g ) was hardly depressed. Electronic devices encapsulated with the dispersed acrylate rubber‐modified epoxy molding compounds have exhibited excellent resistance to the thermal shock cycling test and have resulted in an extended device use life.