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34 SMT007 MAGAZINE I NOVEMBER 2026 its core, it is a conductivity measurement. A circuit board or assembly is submerged in a mixture of isopropyl alcohol and deionized water, and any soluble ionic residues are extracted into the solution. As ions dissolve into the solvent, the conductivity increases. The instrument converts this conductivity change into a reported value expressed as sodium chloride equivalents. This is an elegant concept because conductivity measurements are fast, inexpensive, and easy to perform. A ROSE test can typically be completed in minutes, making it attractive for production environ- ments where rapid feedback is essential. The key point, however, is that ROSE does not directly measure failure risk. It's important to under- stand that it measures the conductivity of an extract solution and uses that measurement to estimate the amount of ionic contamination that was removed from the assembly. What ROSE Testing Does Measure ROSE testing is effective at answering one specific question: How much soluble ionic material was extracted from this assembly? The result provides a bulk indication of soluble contamination. In other words, it tells us whether the overall process appears to be introducing more or less extractable ionic residue over time. This makes ROSE particularly useful for moni- toring the consistency of the cleaning process and tracking contamination trends to support statistical process control (SPC). When a cleaning process has been properly validated, ROSE can serve as an early-warning system. A sudden increase in ROSE values may indicate rinse problems, chemistry concentration issues, maintenance concerns, or contamination entering the process. In short, ROSE is very good at telling us when something has changed. What ROSE Testing Does Not Measure This is where confusion often begins as ROSE does not identify individual contaminants. Unlike ion chromatography, it cannot distinguish chloride from adipate, sodium from ammonium, or a benign residue from a highly corrosive one. Everything is converted into a conductivity measurement and then reported as sodium chloride equivalents. T H E C L E A N T R U T H