Studv Of Mechanism Of Sputtering Metallization For Sensitive Ceramic And Its Application

Sensitive ceramics have become indispensable as new electronic components in the current electronic systems. One of the key technologies in sensitive ceramics is the preparation of electrodes on the surface of ceramics during manufacturing electronic components. China, as one of the biggest countries for sensitive ceramics production, takes up more than one-third of the gross production in the world. However, the domestic production of sensitive ceramics is not quite satisfying:the whole ceramics industry, including foreign-owned enterprises like TDK, TKS and Siemens, continues to use out-dated methods for metalization, such as the screen-burning process, plating process or thermal spraying method. These methods all have high cost and cause low-quality metallization and severe environmental problems. Therefore, it is becoming one of the top research subjects in the sensitive ceramics field to develop new technology and process for preparing the electrodes of ceramics.This paper theoretically analyzes the interface reaction mechanism and ohmic contact mechanism between the electrode and sensitive ceramic such as ZnO varistors and NTC. Also the mechanism of the electrode withstand lead-free solder corrosion is studied. Using magnetron sputtering technique, we developed a series of multilayer electrodes to metalize the NTC ceramics, PTC ceramics and ZnO varistors. Besides, we have developed the large-scale production line and realized in many companies. The main research work is as follows:1. We explore the interface reaction mechanism and ohmic contact mechanism between the electrode and sensitive ceramic by combining the theories of thin film growth, surface physics and metallography. The surface composition of the phases formed by oxidizing reaction at the Cr/ZnO interface has been investigated by means of XPS. The experiment results indicated that the oxidation states of chromium were formed during initial chromium deposition at room temperature, which was an evidence of interface reaction; then they totally turned to become the metallic states of chromium with the increase of coverage. The interface reaction was important for the ohmic contact and adhesion of the electrodes and could prevent the longitudinal diffusion of Ag or Cu. Since few papers have discussed the interface mechanism of sputtered electrodes and the surface of ceramics, this study provides some theoretical basis to reveal the interface mechanism of ceramic metallization, which is affirmed by the industry. The research results were published at the13th National Film Conference and indexed by El journal.2. Through theoretical analysis and comparing a large number of experiments, we designed and prepared different kinds of electrodes on the surface of the NTC ceramics, PTC ceramics and ZnO varistors, respectively. To be specific, this section of work is divided into the following three parts.2.1ZnO varistors usually undertakes large surge current when they are used in protection circuits. To solve this problem, we creatively proposed an electrode combined by Cr and Cu. In this electrode, Cr is used as the buffer layer, which could take oxidation reaction on the surface of ZnO varistors to reduce contact resistance effectively and enhance the binding force of the electrode markedly. Cu is used as the intermediate layer and solder layer, which have low electrical resistivity and good weldability. The experimental result shows that the adhesion force of electrode is larger than10.8MP and the electrode can withstand360℃high temperature melting lead-free solder corrosion. Moreover, the electrical parameters of the ZnO varistors with the Cr+Cu electrode such as U1mA, nonlinear coefficient, leakage current and flow capacity are better than the one with Ag electrode by baking silver.2.2Since NTC ceramics always work under-50℃-200℃, the metal ions can easily diffuse into the ceramic body and the electrode can be easily oxidized. Analogously, we deposited multi-layered Ni-V+Ag electrode on the NTC ceramics surface, where Ni-V films as the transition layer and barrier layer of the electrode and Ag films as the welding layer of the electrode. The results showed that the Ni-V film is helpful for forming good ohmic contact with the surface of NTC ceramic and enhances the adhesion force of the electrode remarkably. Besides, Ni film could stop Ag from diffusing into the body of NTC ceramic and thus avoid the weakness of the baking silver electrode. The Ni-V+Ag electrode also has high-temperature resistance to the corrosion due to its no-lead soldering, which guarantees the good soldering of the electrode.2.3We prepared multilayer Cr+Ni-Cu+Ag electrode on the PTC ceramics surface and realized mass production of this electrode. Production result has shown that Cr+Ni-Cu+Ag electrode is only one twelfth thick as baking silver electrode and provides strong combination, low contact resistance, good weldability, low cost and strong resistance to high-temperature solder corrosion.3. Finally, we participate in industrial production based on our laboratory experiments, including design and manufacturing the large-scale production lines and debugging and installation of this equipment. At present, the technology and production line has been applied in a number of foreign and private enterprises, which could reduce the cost by76%and save the power consumption by48%. In the field production, using magnetron sputtering technology to metallize sensitive ceramics has eradicated pollution and achieved really green manufacturing. Therefore, this technology has reached international advanced level and is creating significant social and economic benefits.