Study On Ultrasonic Bonding Of Copper Foils

Interfacial joining mechanism of ultrasonic connection in m icroelectronic devices and high power devices has become to the key issue for limiting the innovation of the ultrasonic mental welding technologies and equipment, and directly affecting accurate recognition of reliabilities. Therefore, clarifying the characteristics of connected interface and exploring the process and reason of the interface formation are of great significance to guide the development of ultrasonic technologies and enhance the quality of devices connected by ultrasonic method.In this paper, the copper foil with 100 μm thickness was the object of study, and the interfaces of connections were observed. This paper has analyzed the morphology of connected interface and compared the morphology wi th different preset parameters, then ascertained the suitable preset parameters. The analysis of frictional process has optimized the process of connection. From mechanical angle, analyze mechanical feature of the connected system when the ultrasonic was working and explore the formative reasons of different processes. In the respect of energy, try to evaluate the quality of joints. To summarize the changes of copper grain crystal, the grain crystal size and misorientation was analyzed. Designing required process of anneal to make the grain grown and profile the occurrence of metallurgical process is the innovation point.Different morphologies was observed in the figures of light microscope and SEM. The changes of interfaces can be observed if the parameter s of welding force and amplitude were changed. The welding force and amplitude were a couple parameter that needed be matched and effected the morphologies together. The suitable parameters were ascertained. In theoretical analysis, supposing the friction factor to get the relationship of friction force to clarify the friction process. The expectant process can be occurred by using the relationship of friction force. To get the conditions of synchronous movement between the sonic tip and copper foil, the interface between them was studied by using Tresca yield limit condition.The crystallographic study of ultrasonic connection has analyzed the statistical result of grain size. The results show that the distribution area of grain size was in a trend of decreasing and the grain size near the interface was smaller than that in copper foil. The analysis of statistical result of grain misorientation shows that the distribution area of grain orientation was larger and there was no evidence of grain misorientation in interface and copper foil. Anneal connected copper foil on designed parameters then analyze the grain EBSD picture. According to the difference growing of grain between interatomic connections and no connections, findings that perforative grains existed in interface proved that uncertain size micro-melting has happened during the process of connection.