Microwave copper-clad plate preparation method capable of keeping low thermal expansion coefficient in three axes at the same time

The invention discloses a microwave copper-clad plate preparation method capable of keeping a low thermal expansion coefficient in three axes at the same time. By means of the method, a low thermal expansion coefficient of a dielectric plate can be kept in the X axis, the Y axis and the Z axis at the same time. The method includes the following steps that 1, bonding sheets are prepared, wherein fluororesin is added into PTFE emulsion for modification, and mixed ceramic powder/particles, reinforced fibers and a surface modifier are added; then the mixture is diluted into several parts of bonding sheet solutions with different concentrations with deionized water, and the bonding sheet solutions are stirred to be uniform; PTFE porous films are dipped into the uniform bonding sheet solutions with different concentrations, and dipping sheets are adjusted to have a preset thickness; moisture and low-temperature volatile matter on the dipped porous films are removed, drying is carried out to achieve film formation of the fluororesin, and the uniform-thickness bonding sheets with smooth surfaces are obtained; 2, the bonding sheets obtained in the step 1 are overlapped, the number of layers of the bonding sheets is controlled according to the requirement for the thickness of the copper-clad plate, metal foil is placed on the upper layer and the lower layer, and vacuum lamination is carried out.