INVESTIGATING MASS IMAGING LEAD FREE MATERIALS USING ENCLOSED PRINT HEAD TECHNOLOGY

摘要

Within the Surface Mount Assembly (S.M.A.) process, solder paste is primarily used as a mechanical and electrical connection. Solder paste is generally deposited using a mass imaging process, such as squeegees, however this paper will utilise the enclosed print head technology. The process associated with mass imaging is a critical and demanding stage in the soldering phase of S.M.A. It has been documented many times that this process contributes more than 60% of all S.M.A faults; This being the case it illustrates the requirement to have a full comprehension of the mass imaging process. With legal and commercial pressure put on to remove lead from within the electronics sector, the solder paste alloy is obviously under review. Much work is being carried out on the metallurgical properties of these lead free solder pastes such as joint strength and compatibility within the manufacturing process. However, this paper will focus on investigating the process window for mass imaging of lead-free materials. The major influences within the mass imaging process have been documented in numerous studies using lead rich materials. However, the material used to replace the Pb component changes the solder paste properties and therefore the characteristics of the print medium. Therefore to conduct this study a two level three factor Design of Experiments with center points will be utilised .The factors investigated in this paper will be print speed, paste pressure and separation speed. Three material suppliers will be used to ensure the results givea broad representation of the significant effects on the process window. Comparison to a lead rich material will also be carried out to allow an evaluation to be concluded. Each pate will be tested for paste release transfer efficiency using the optimum setting concluded from the characterization stage.