Microwave dielectric ceramic is used in microwave (mainly 300MHz ~ 30GHz frequency band) circuit as a dielectric material and perform one or more functions of the ceramic, used in modern communications as resonators, filters, dielectric substrates, media Antenna, dielectric waveguide circuit, dielectric ceramic microwave circuit used in addition to the necessary mechanical strength, chemical stability, it should also meet the following dielectric properties, microwave frequency relative permittivity C ^ 2 high Q · f value and frequency temperature coefficient close to zero Microwave dielectric ceramics can be classified according to their composition system, dielectric properties and application fields. The more common ones are classified according to the dielectric constant, which can be classified into low dielectric constant (20-40), dielectric constant type 40 ~ 80); high dielectric constant (> 80). Low dielectric microwave ceramics are mainly used in microwave substrate, satellite communications and military applications such as communications systems. At present, more low-microwave ceramics are mainly based on the application of AL2O3 and AIN. The ideal performance of the low-microwave ceramic based copper-clad insulation materials is that they have good thermal conductivity, good heat dissipation and high frequency microwaves Produced under the loss as small as possible. BeO ceramic is an excellent material for insulating heat dissipation in ceramic-based CCLs. However, due to the toxicity of BeO powder, strict protection measures are required in the manufacturing process, and BeO ceramics have been banned in developed countries such as the United States and Japan. Therefore, the development of alternative BeO ceramic CCL with a new insulation material is imminent. AIN ceramic is a kind of ceramic material with good thermal performance and nontoxicity. Its theoretical value of thermal conductivity is 320W / (m · K), which is close to the theoretical value of thermal conductivity of BeO ceramics of 370 W / (m · K) And AIN ceramic materials have been developed with a thermal conductivity above 200 W / (m · K). Therefore, AIN ceramic material is considered as the most promising alternative to BeO ceramic insulation materials. Due to the small dielectric constant of BN, h-BN is added to AIN ceramic. Based on the dielectric constant formula of the multi-phase material, adding h-BN to AIN can also reduce the dielectric constant of AIN ceramic. The purpose of this paper is to develop AIN and BN-AIN based ceramic materials with high thermal conductivity and low dielectric loss to meet the requirements of ceramic CCL to replace BeO ceramic materials. Because BN, AIN are covalent compounds, difficult to sinter, in order to obtain high density ceramic, need to add sintering aids. The choice of sintering aids should be considered from two aspects, one is that it can form a low-melt phase to achieve liquid-phase sintering and promote densification; secondly, it can react with oxygen impurities in AIN to purify the AIN lattice. Based on these two points, the choice of Y2O3 sintering aids. Since Y2O3 forms Y3AI5O12 with alumina on the surface of AIN, the liquidus temperature of Y3AI5O12 is 1760 ° C, which promotes sintering and purifies the crystal lattice. However, if the sintering aids are not uniformly dispersed, it is difficult to fire a densely packed ceramic material. Through the chemical process, the BN is wrapped onto the surface of the AlN powder so as to achieve the purpose of evenly dispersing the BN into the AIN matrix, and the composite microstructure of the composite powder is used to prepare the multi-phase ceramic with the microstructure uniform and the thermal conductivity thereof is 78.1 W / (m · K), a dielectric constant of 7.2 in the Ka band, and a minimum dielectric constant of 13 × 10 -4. By studying the microwave characteristics of AIN and BN-AIN-based composite ceramics in Ka wave band, it is found that the dielectric constant of AIN-based ceramic material changes little with frequency, but the dielectric loss of the material varies greatly with frequency, and There is a maximum and a minimum in this interval.