Surface Mount International Conference Proceedings


Author: Christina L. Sharp
Company: Eaton Corporation
Date Published: 9/10/1996   Conference: Surface Mount International

Abstract: Control of solder paste is a problem for contract manufacturers and electronic assemblers. The solder paste user is at the mercy of the manufacturer when following recommendations for the usable time window for the best process and reflow results. In addition, the receipt of incorrectly formulated paste or paste that has been mishandled, whether by shipping or by packaging, will not be detected until PWB’S have been assembled and inspection-ready. The control of solder paste is essential. Troubleshooting a surface mount process due to poor solder paste performance is impractical if the cause/effect of paste failure modes is unknown. The overall result of poor solder paste performance is costly rework. It was theorized that an understanding of the material property of solder paste could be used as an in-line process control tool to determine solder paste workable life in production. In April 1994, EMPF coordinated an industry/government/academia consortium to develop a process-control system using AC impedance spectroscopy. The 1S4000 is the developed process control tool. The 1S4000 was implemented at the company’s manufacturing facility as an in-line Beta site process control tool. The production staff were trained, the process was altered to incorporate the 1S4000, and data was collected. This data was used to analyze the solder paste performance. The data collected supported that solder paste is traceable. The data is being analyzed to explain past theories of solder paste failure modes. It is theorized that the 1S4000 data acquisition system will be able to proactively determine the solder paste failures. This paper will explain how this tool was incorporated into a surface mount production line, that solder paste failures are traceable, and that the failure modes of the solder paste were explained by the data collected. KEYWORDS: Solder paste, AC impedance spectroscopy, Process control

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