Issue link: https://iconnect007.uberflip.com/i/976095
40 SMT007 MAGAZINE I MAY 2018 Those in favor of continuing to utilize ROSE for process control might argue that it can and does meet the attributes in the definition. However, the bigger question that we pose today is does ROSE do so across all product types, designs and material sets? In our opin- ion, the answer is definitively no. Having analyzed the cleanliness of assem- blies for over 50 combined years, we can say one thing with absolute certainty: Not all assemblies have the same threshold of tolerance for process residues. Some assem - bly designs are far less tolerant than others. Considering the industry's drive towards reducing board real estate and increasing population density, then naturally there is a need for a more rigorous method for under - standing what is lurking just on the surface. A bulk-solvent residue measurement from a 50-year-old methodology no longer meets the need, at least not across all industry segments. We cannot hope to achieve the level of under - standing we need, related to the impact of our process residues, from a method that has not changed since the 1980s, when bulk-volume testers became the norm. "I was asked how well the current ionic contamination method works for determin - ing acceptable limits of contamination. ROSE (omega meter) definitiely does not do a good enough job of detecting ionic contamination on PCBAs. The current IC and SIR methods do not support volume production monitor - ing of real-time contamination feedback. The ROSE is obsolete, IC is the next best, and ulti- mately, we need a better test method," says Mark Talmadge, director of manufacturing at IEC Electronics. In addition, the IPC task groups responsible for that method have not addressed its limita- tions and have not done their due diligence in keeping the method on par with the industry trends. This is not a slam towards those task groups. They are, after all, comprised of volun- teers that have real jobs to focus on. However, we can't afford to be complacent any more. Our methods must attempt to keep pace with technology or we run the risk of gathering data that gives only a partial picture or worse, noth- ing of value at all. What is the alternative? Since we are dealing specifically with ionic residues in this article, there is currently one tool that has both attri- butes described earlier and is primed for eval- uating the ionic residues of modern assem- blies—ion chromatography (IC), an accurate and repeatable tool. The volume of solvent used for an extraction can be substantially less. However, it is not without its limitations. IC is not particularly well-suited for operation on the production floor. It requires more qual - ified individuals to run it and to interpret the results and it currently uses the same solvent as ROSE. While there are some needed modi- fications with the IC method and equipment, we believe it is by far the best tool for track- ing, investigating and monitoring the levels of ionic residues on your PCBs, PCBAs and even components (for you GEIA-STD-0006 folks). If you would like to participate in advanc- ing the cleanliness measurement technology, or have any questions or suggestions, please feel free to contact us. SMT007 Joe Russeau is president and CEO of Precision Analytical Laboratory. To contact Russeau with questions or comments, click here. Mark Northrup is VP of Technology with IEC Electronics. Figure 3: A representative example of a standard anion chromatograph.