Development of high reliability and high processability thermosets for electronic packaging applications based on ternary systems of benzoxazine, epoxy and phenolic resins

We have developed new polymeric systems based on the ternary mixture of benzoxazine, epoxy, and phenolic novolac resins. Low melt viscosity resins render void free specimens with minimal processing steps. The material properties show a wide range of desirable reliability and processability which are highly dependent on the composition of the monomers in the mixture. Fourier transform mechanical spectroscopy techniques (FTMS) are utilized as a powerful tool to study the sol-gel transition of covalently bonded polymeric networks. The gelation of the ternary mixture shows an Arrhenius-type behavior and the gel time can be well-predicted by the Arrhenius equation.;The synergism in the glass transition temperature of these ternary systems is also reported. The molecular rigidity from benzoxazine and the improved crosslink density from epoxy contribute to the synergestic behavior. The mechanical relaxation spectra of the fully cured ternary systems in the temperature range of -140°C to 350°C show four types of relaxation transitions i.e. gamma, beta, alpha1, and alpha2-transitions. Thermal conductivity of the molding compounds based on these ternary mixtures exhibits a very high value of about 27 W/mk in aggregate-type boron nitride filler and the value of about 8.6 W/mk in flake-like crystal boron nitride filler comparing at the same filler loading of 68% by volume. The presence of epoxy resin in the ternary systems is found to provide improvement in a high temperature adhesion.;The curing kinetics based on dynamic DSC results of this ternary system show nth order kinetics with an overall reaction order of 1.5 having activation energy of 111 kJ/mol whereas that of the gelation process is 75 kJ/mol. Thermal degradation process of this resin is deceleratory type with activation energy of 185 kJ/mol. A choice of a resin used for the study can provide maximum Tg of about 220°C in its fully cured specimen. The system has a potential use as high performance electronic packaging molding compounds or highly filled systems.