Heat dissipation has become a key problem for highly integrated and miniaturized electronic components. High thermal conductivity, good flowability and low coefficient of linear thermal expansion (CLTE) are indispensable performance parameters in the field of electronic potting composite materials. In this study, spherical alumina (Al2O3) was surface modified by γ-(2,3-epoxypropoxy) propyltrimethoxy silane (KH560) and γ-aminopropyltriethoxy silane (KH550) and labelled as Al2O3-epoxy and Al2O3-NH2, respectively. Al2O3-epoxy and Al2O3-NH2 powders were equally filled in vinyl silicone oil to prepare a high Al2O3 loading (89 wt%) precursor of silicone potting adhesive. The viscosity of the precursor rapidly decreased with increasing reaction time of Al2O3-epoxy and Al2O3-NH2 at 140 °C. The viscosity reduction mechanism may be due to the formation of some Al2O3 clusters by the reaction of Al2O3-epoxy with Al2O3-NH2, which results in some vinyl silicone oil segments being held in the channel of particles through capillary phenomenon, leading to the friction among Al2O3 clusters decreasing considerably. Laser particle size analysis and scanning electron microscopy (SEM) results confirmed the existence of Al2O3 clusters. Energy dispersive spectroscopy (EDS) and dynamic viscoelasticity experiments revealed that some segments of vinyl silicone oils were held by Al2O3 clusters. When Al2O3-epoxy and Al2O3-NH2 reacted for 4 h, the thermal conductivity, CLTE and volume electrical resistivity of the silicone potting adhesive reached 2.73 W m-1 k-1, 75.8 ppm/°C and 4.6 × 1013 Ω cm, respectively. A new strategy for preparing electronic potting materials with high thermal conductivity, good flowability and low CLTE is presented.
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