Study On Preparation Technology Of Alumina Ceramics For Microwave Shell

The great importance of development of microwave devices due to technology improvement of microwave packages. Microwave packages have the special effects of mechanical support, electrical interconnection and environmental protection for the chip of packaging, and play the key roles in microwave signal transmission, cooling channel, electromagnetic shielding, signal processing, power management for the entire device (module) and so on. The parasitical parameters of package directly determine the performance of devices and circuit, and have direct working involvement of devices and circuit modules. The relation between microwave packages and device chip is that of body and viscera.Dielectric materials have significant function on development of microwave packages. Take example for IB power transistor package, which uses the structure of the metal wall-ceramic insulator, and alumina ceramic is used as the dielectric material. The performances of ceramic insulator directly impact the performance indicators of microwave devices, and the transmission loss of the microwave signal is directly determined by insertion loss and voltage standing wave ratio. In order to meet the later development of microwave package, the dielectric loss of alumina ceramic is lower through improvement and optimization of processing techniques of ceramics, and achieving the aim of the study. Then the actual applying and assessment which is used for microwave packages are researched by the HTCC process.The circuit structure of IB package in the wave band were designed and optimized with HFSS method which was a 3D electromagnetic simulation software. The microwave transmission characteristics of 50? transmission port were effectively improved through adding high inductance compensation structure and inserting transition structure between microstrip and stripline, while the insertion loss and voltage standing wave ratio were reduced. The resonance of the wave band was eliminated throng structure optimization and size control of internal shape of package. Finally, two good simulation results had been obtained, one was that the insertion loss was less than 0.3dB at the band, and the other one was that voltage standing wave ratio was less than 1.3. Those performances of actual product were measured, by compared with the results of experiment and calculation, it can be concluded that calculated results agreed well with the experimental results.Base on the theory and method of structure and thermal design of package, the models of structure and thermal analysis of two kinds of packages have been established by the finite element analysis software ANSYS. The structure stress analysis of IB package in brazing conditions and thermal simulating analysis of typical high power chip packaging were performed respectively. Stress distribution of optimized package was investigated by the method that the factors of floor structure, framework size, fit tolerance and cooling condition were adjusted. Results show that the maximum stress was reduced to 201MPa, and the highest temperature of chip which is working at rated power was 147?, the package could satisfy the demands of cooling requirements of device at working normally.