Surface Mount International Conference Proceedings


Author: D. Verbockhaven
Company: Air Liquide - CRCD
Date Published: 9/10/1996   Conference: Surface Mount International

Abstract: As a response to the more and more stringent demand in terms of increasing quality requirements, production flexibility and cost reduction, the assemblers wish to adapt at best their soldering processes. In this context, the atmosphere is often regarded as an important parameter. The selection of a soldering atmosphere, usually characterized by its oxygen content may involve changes in the process, ranging from variations in the defect level to the ability to use new types of fluxes or to suppress the cleaning step. Each of those improvements influences the global c@ with an amplitude which depends on the composition of the atmosphere considered. In order to ease the approach to the atmosphere global optimization a precise analysis of the wave and reflow soldering processes was started. It led to a segmentation in expenditure items, including the raw materials, manpower and the investment amortization. A survey on the costs for each expenditure item, and on the influence of the atmosphere composition, was performed. Information was retrieved using assembler’s experiences and data from suppliers. Extensive technical studies were performed to quantify more precisely the influence of the atmosphere composition. The study led to the establishment of a spreadsheet listing all the expenditure items involved in a procedure of atmosphere global optimization. A complete guide providing data on the modifications involved by the atmosphere change was also realized. All those elements, which are presented in this paper, provide help to analyze a soldering process and to obtain an idea of the optimum point of use. When applied to standard cases, the conclusions can be the followings: . The use of a nitrogen based atmosphere is always cost effective if it enables to suppress the cleaning step, whatever the cleaning type is. . When there is no modification of the process, a difference between wave and reflow must be done. For wave soldering, an atmosphere containing less than -500 ppm Oz is generally the best solution, whereas for reflow, the optimum atmosphere may range between 1°/0 02 and 10 ppm 02, depending on the flux type.

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