Reserch On The Welging-ability Of RF-multilayer Chip Inductors

Components welding ability is a general concept. The performance of components welding not only show great influence on device common performance, such as bonding pad size, welding layer structure and component parts, but also has direct connection on soldering, welding technology, usage of working environment and process. Research on the welding ability of RF multilayer chip inductor is based on the demands of surface mounting technology(SMT). This thesis, written from the aspect of manufacturing technique, is about to explore effects of three layer coating structure and components on welding ability. Besides, it can also provide technical base for RF-MLCI. Meanwhile, it is also a reference to the connection of upstream and downstream integration of components industry.Firstly, the welding ability principle and SMT welding technology has been studied in this thesis, and the evaluation items and research methods for devices are established according to IPC, GJB and so on. The discussion of material, structure and manufacturing technique of RF-MLCI& RF-MLCF, especially the form and function of three layer coating structure, are introduced in the thesis. Furthermore, we use three layer coating(silver layer, nickel layer, tin layer) structure parameter such as thickness and shape as main variants to study the influence of above parameters on welding ability of devices.The results indicate that a certain thickness of metal composite layer is the basis of welding function. The morphology of three layer coating structure shows great influence on welding ability, especially the reliability of device. The further investigation shows that the three layer coatings exhibit strong interactions reciprocally and a good outer layer can be as a shelter to inner layer. Moreover, the poor morphology of inner layer can be transfer to outer layer, and this phenomenon happens more obviously in deep inner layer structure.Silver layer as a plating substrate, its density is determined by the silver paste composition and firing conditions and it is necessary to balance amount of glass and holes in the layer. The superfluous glass can lead to make coating layer thin, poor welding; and lack of glass have resulted in the penetration of plating solution, bad stress, low mechanical strength and other issues. Intermediate plating nickel layer is a barrier layer between two layers of metal, plays mitigation of adverse effects between the intermetallic compounds(IMC) formed, and improves the deposit bottom topography at the same time. An outer plating layer of tin or tin-lead is a direct carrier of the welding function; its thickness, morphology; impurities broadly affect the welding performance. When a dense plating layer reaches a reference thickness, simply increasing the thickness of the plating layer can not linearly improve welding performance. Good density of plating layers is the key to long-term welding reliability guarantee. Density of plating layers is related to plating solution system, plating current, solution impurities, plating barrel and other factors, and these factors are required for complex test and adjustment.