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|The Cleaning Effectiveness in Electronics Assembly Process|
|Keywords: flux removing, cleaning efficiency, ultrasonic and spray cleaning|
|This paper deals with research and development of the cleaning methods efficiency in the area of electronics assembly technologies, target the cleaning after lead-free soldering. Any contaminants as ionic or non-ionic flux residues, etching residues, handling contamination, fingerprints etc. can cause a decrease of lifetime and fatal failures in future time. Therefore cleanliness is only the way to achieve and to assure acceptable reliability of produced electronic systems. Increased miniaturization, higher speeds and tighter board space highlights that need, as well as request for higher reliability, especially by some type of applications (automotive, medical, military etc.). In more with introduction of new environmental regulations (WEEE, RoHS) and eco-design (EuP) rules the cleaning becomes to be more and more important for various parts of technological processes, including lead-free soldering. Correct adjustment of the cleaning process may save as the time as well materials consumption. Cleaning process efficiency very much depends on physical conditions under which the cleaning runs. The base of our work makes analyzing of principal agitation methods during the cleaning process in the electronics assembly production process. The special test pattern on glass substrate were designed and realized to become a “scale” for measuring cleaning efficiency. Several experiments have been done to compare efficiency of ultrasonic agitation with other methods like spraying in air, spraying under immersion etc. There were three different methods for contamination measurement applied, the first with standard contaminometer, and two based on optical principle. Results and conclusions are derived on the base of statistical valuation. Development and testing of test-pattern enables to use that evaluation method like some kind of “external calibration” for cleaning process or in case of need directly for cleaning equipment. In general the cleaning process, being a result of many factors, is very difficult to be described with quantitative expressions. Testing substrates, which has been designed and tested, enable to compare different cleaning processes and also a real cleaning process with ideally running process in the same equipment. The environment impact of the cleaning process on the SMT production line is observed linked to legislative rules. The aim is to establish objective criteria for the selection and optimization of cleaning process and equipment, as from the point of view of cleaning efficiency, as well as the operating costs and environmental impact.|
|Ivan Szendiuch, Assoc. Prof.
Brno University of Technology
Brno, Morava 602 00,