Physical Confinement via the Framework of Mesoporous Silica Filler: A Strategy for Improving the Comprehensive Thermomechanical Performance of Epoxy-Based Composites

How to solve the challenge of balancing the lower coefficient of thermal expansion (CTE), good toughness, and suitable modulus is a thorny problem in SiO 2 /epoxy (EP) composites especially used in electronic packaging, such as underfill, EP molding compound, die-attached film, and so on. Herein, the monodispersed mesoporous silica particles (MSPs) are proposed as a substitute for conventional silica fillers into EP composites. The mesoporous silica framework provides physical confinement to polymer segment mobility, while strong interfacial interactions between the MSPs and the polymer enable simultaneous improvements, including significant reductions in CTE values, lower storage modulus, and enhanced fracture toughness. Furthermore, the introduction of the pores in the MSPs results in a lower dielectric constant and reduced dielectric loss in the X-band. Besides, as compared with the nonporous silica particle-filled EP composites, nearly 10 wt % of filler loading is saved in MSPs/EP composites, which also provide a great convenience for process operation. Thus, this study has provided an advanced approach for the development of high-performance SiO 2 /EP composites for use in electronic packaging.