▎ 摘　　要

NOVELTY - Microwave composite dielectric substrate comprises 30-80 wt.% inorganic filler comprising high thermal conductivity inorganic fillers and additive inorganic fillers, 1-10 wt.% glass fiber, 10-70 wt.% fluororesin polymer system comprising PTFE, 0.1-2 wt.% coupling agent comprising silane coupling agent and 0.1-5 wt.% ester surfactants, where the high thermal conductivity inorganic filler comprises aluminum nitride and additive inorganic fillers comprises silica. USE - The dielectric substrate is used in high-tech fields such as communication, radar, satellite, high-speed rail, aircraft, and high-tech weapons and equipment. ADVANTAGE - The dielectric substrate has high thermal conductivity and high thermal stability, achieves dielectric constant of about 2.56.5, temperature coefficient of dielectric constant of about 10 ppm/ degrees C, and coefficient of thermal expansion of less than 24 ppm/ degrees C, and the thermal conductivity is 1.2 W/mx k, and the method is simple, environmentally friendly, convenient and beneficial for industrialized production. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a method for preparing a microwave composite dielectric substrate involving (i) surface modifying glass fiber with coupling agent by dissolving the coupling agent in anhydrous ethanol solution, stirring for 20-60 minutes under the condition of 50-150 rpm of the mixer, adding the glass fiber to the coupler, continuing stirring for 30-180 minutes at the speed of 80-200 rpm in the ethanol solution of the coupling agent and drying it in an oven at 65-125 degrees C for 2-10 hours, (ii) performing surface modification treatment of the inorganic filler with coupling agent by dissolving the coupling agent in anhydrous ethanol solution, stirring for 20-60 minutes under the condition of the mixer speed of 50-150 rpm, adding inorganic filler into the ethanol solution of the coupling agent, continuously stirring for 30-240 minutes under the condition of the mixer speed of 100-200 rpm and drying it in an oven at 85-135 degrees C for 2-10 hours, (iii) placing the modified glass fiber and inorganic filler into a ball mill for mixing and stirring for 30-240 minutes under the condition of rotating speed of 100-300 rpm, (iv) adding ester surfactants to the reactor filled with deionized water, stirring to dissolve, adding the mixed glass fiber, inorganic filler and fluororesin polymer system to the reactor in turn at 30-80 degrees C, completely stirring for 60-240 minutes under the condition of rotating speed of 80-250 rpm to obtain the mixture, (v) placing the mixture obtained in the step (iv) into an oven for drying, adding booster with a mass fraction of 5-30% of the mixture to the dried mixture, completely stirring for 30-240 minutes under the condition of the rotating speed of the mixing mixer of 80-300 rpm to obtain the composition, (vi) placing the composition obtained in the step (v) into a mold and transferring it to a vacuum isostatic pressing equipment for pre-forming with a pressure of 5-100 MPa to obtain a green composition, (vii) extruding and forming the green composition obtained in the step (vi) at 50-200 degrees C under a pressure of 1-20 MPa to obtain a green substrate, and (viii) coating the green substrate obtained in the step (vii), transferring it to the vacuum laminator at 80-390 degrees C, hot-press sintering for 120-240 minutes under the pressure of 4-20 MPa to obtain a microwave composite dielectric substrate product.