The Preparation Technology Of Multilyer Chip Varistor

With the development of electronic information industry, the electronic components are developed in the direction of miniaturization and low working voltage, and the miniaturized chip voltage-sensitive varistor are developing rapidly in recent years accordingly. As far as the size of multilayer chip varistor concerned, compared with products produced by foreign company with size of 0603(0.6mm * 0.3mm), the internal products remain a large size of 1005(1.0mm * 0.5mm). Due to the restriction of materials for varistor production and producing process of devices, the internal technology for varistor production needs to be further developed.Multilayer chip varistor has advantages such as small size, low working voltage, high reliability, flexible installation and so on, and mainly used in overvoltage protection circuit applications. In this paper, the research focuse on the material, device structure designing and fabrication processes of the 0603 type multilayer chip varistor. The main contents are as follows:(1) Based on the main structure design and internal electrode structure design of multilayer chip varistor, the influence of different structural design on device properties has been studied. Accordingly, the different internal structure design has been demonstrated to satisfy the different capacity requirements of multilayer chip varistor in circuit applications.(2) The metal oxide of Bi2O3, Sb2O3 are composited into ZnO matrix as voltage-sensitive ceramic materails, and the perforamce of this composite is investigated. The influence of different ratio material on performance of multilayer chip varistor is studied. Furthermore, the inner electrode conductor of varistor and synergistic effect between inner electrode conductor and voltage-sensitive ceramic maerails has been investigated.(3) The influence of key producing processes on electric performance and reliability of devices is studied, and the main problems and solutions during the slurry preparation for multilayer chip varistor production are explored. The advantages and shortcomings of three kinds of film forming process, waterfall cast printing molding method, cast film forming method and overlap printing method are investigated, and the optimized producing process are explored. The process for voltage-sensitive ceramic materails and inner electrode conductor cofired is explored. The influence of material shrinkage ratio and atmosphere during cofired process on electric performance of devices has been investigated. Furthermore, the influence of terminal electrode preparing method and surface treatment methods on electric performance, appearance and reliability of devices has been studied in detailed.