A study on the viscosity reduction mechanism of high-filled silicone potting adhesive by the formation of AlO clusters.

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 (AlO) was surface modified by γ-(2,3-epoxypropoxy) propyltrimethoxy silane (KH560) and γ-aminopropyltriethoxy silane (KH550) and labelled as AlO-epoxy and AlO-NH, respectively. AlO-epoxy and AlO-NH powders were equally filled in vinyl silicone oil to prepare a high AlO loading (89 wt%) precursor of silicone potting adhesive. The viscosity of the precursor rapidly decreased with increasing reaction time of AlO-epoxy and AlO-NH at 140 °C. The viscosity reduction mechanism may be due to the formation of some AlO clusters by the reaction of AlO-epoxy with AlO-NH, which results in some vinyl silicone oil segments being held in the channel of particles through capillary phenomenon, leading to the friction among AlO clusters decreasing considerably. Laser particle size analysis and scanning electron microscopy (SEM) results confirmed the existence of AlO clusters. Energy dispersive spectroscopy (EDS) and dynamic viscoelasticity experiments revealed that some segments of vinyl silicone oils were held by AlO clusters. When AlO-epoxy and AlO-NH reacted for 4 h, the thermal conductivity, CLTE and volume electrical resistivity of the silicone potting adhesive reached 2.73 W m k, 75.8 ppm/°C and 4.6 × 10 Ω cm, respectively. A new strategy for preparing electronic potting materials with high thermal conductivity, good flowability and low CLTE is presented.