FLUID FLOW MECHANICS: KEY TO LOW STANDOFF CLEANING
Authors: Harald Wack, Ph.D., Umut Tosun, Naveen Ravindran, Sylvain Chamousset, Joachim Becht, Ph.D., and Steve Stach Date Published: 5/19/2011
Abstract: In recent years, various studies have been issued on cleaning under low standoff components; most however, with incomplete information. It is essential to revisit and describe the latest challenges in the market, identifying obvious gaps in available information. Such information is crucial for potential and existing users to fully address the cleanliness levels under their respective components. With the emergence of lead-free soldering and even smaller components, new challenges have arisen including cleaning in gaps of less than 1-mil. This study was initially designed to investigate the impact of mechanical vs. chemical energy contributions during the removal of contamination under 1-2 mil standoff components. To validate the results obtained, extensive studies were conducted, specifically prepared testassemblies, iterative experimentation, as well as new mechanical innovations that might help users in the future. The latter include, but are not limited to, various flow pattern designs and industry-leading cleaning agents. As a result, the authors will also include experimental data to address fluid flow mechanics, temperature and solvent concentration related effects. Initial results obtained indicate that cleanability of residues under low standoff components has become a non-trivial issue. Not only are residues becoming harder to remove, the penetration of the cleaning agent seems to be in direct relationship with the geometry and height of the components in question.