Metallization Study Of Microwave Dielectric Ceramic Resonators Via Magnetron Sputtering Technology

With its proper dielectric constant, high Q value and excellent temperature stability, microwave dielectric ceramics have been widely applied in various fields, from wireless communication to aeronautics. Kinds of passive components made by the ceramics, such as dielectric capacitor, microwave filter and dielectric antenna, are developing in the trend of high reliability and small size. Urgent demand for high-performance microwave dielectric ceramics has led it to be hotspots in the research of functional material.Microwave dielectric loaded cavity filters which has important application in wireless communication base station, is the best solution to miniaturization of base station filter, but its practical application has been restricted by the small quality value at the moment. Quality factor of microwave dielectric loaded cavity filters is mainly decided by of material's dielectric loss and conductivity loss of metal film. Dielectric loss has been greatly reduced by improvement of material's properties, while there is little studies about conductivity loss of metal film. Metalized film of traditional printing sintered has great loss, which has become a major factor that limits filter's Q values. In this paper, we proposed a method of DC magnetron sputtering metallization on microwave dielectric resonators, whose relative dielectric constant is 45. We discussed the impacts of different cleaning processes and composite membranes on dielectric resonator performance, compared it with traditional silver screen process. The green magnetron sputtering metallization process has positive meaning for manufacture and performance improvement of wireless base station filters, when applied in the field of microwave dielectric filter.The main work and achievements of the paper are as follows:1. Introduced demand for microwave dielectric filter applications and microwave dielectric ceramic surface metallization process in details. Multilayer films magnetron sputtering metallization process was proposed due to shortcomings in traditional silver screen process;2. Studied theoretically performance influences of metal layers with different thickness and different membrane system coated on microwave dielectric resonator surface, such as resonance frequency or Q value. According to simulation results from electromagnetic simulation software HFSS, we found that Cr/Cu/Ag composite film system on microwave dielectric resonator with permittivity of 45 has the best theoretical performance around the frequency of 950 MHz, and theoretical Q value could up to 2720;3. Implemented surface metallization on microwave dielectric resonators via magnetron sputtering process experimentally, discussed performance influences by test data of surface adhesion and quality factor Q in different membrane system with different film thickness. In this paper, we put forward creatively combination method of radio frequency plasma cleaning and low pressure transition metal sputtering to improve bonding force between substrate and films, and ensure the deposition quality of metalized films. Experimental results indicate that binding force of Cr/Cu/Ag composite membrane system is 6.4 MPa after fine grinding and RF plasma cleaning as well as magnetron sputtering, while Q value can be up to 2673, which is far superior to traditional silk screen process with binding force of 1.8 MPa and Q values of 2268.